Return of king Schumacher
MERCEDES (BRAWN GP)
The return of seven-times champion Michael Schumacher, who retired from Ferrari in 2006, is the big story along with Jenson Button's departure to McLaren.
Schumacher, winner of 91 races, showed in testing that he still has the pace, although the Mercedes has not looked the fastest car.
Nico Rosberg, son of former champion Keke, has yet to win a race after four seasons with Williams but is now well placed.
With Ross Brawn in charge, the resources of Mercedes and the presence of Schumacher, the team should again be contenders for both titles but it may be a race or two before they are fully up to speed.
Image: Michael Schumacher returns to F1 circuit
Faith in old warhorses
The only top team with an unchanged line-up, Red Bull won the last three races of 2009 and are a good bet to pick up where they left off.
They look to be on a par with Ferrari after quick times in testing, but will need better reliability than last year. Given Adrian Newey's brilliance as chief designer, expect them to be title contenders again.
Mark Webber has overcome last year's leg injury and, with his contract expiring, is determined to succeed. Sebastian Vettel was runner-up last year and will want to remind Schumacher who is currently the top-ranked German.
Image: Red Bull team with the car
Button teams up with Hamilton
The arrival of Button makes McLaren the first team to start a season with the last two title-holders in their lineup and the first since 1989 with two champions.
That could be a recipe for friction, as well as possibly opening the door for someone else in the title race if they take points off each other.
Both should have a car capable of winning races, and have been assured of equal treatment, and if they do their stuff then McLaren may end the year as constructors' champions for the first time since 1998.
The car has been strong and reliable in testing but there is still plenty of room for improvement.
Image: Lewis Hamilton and Jenson Button
Alonso and Ferrari an irresistible combination
New arrival Alonso and Ferrari look an irresistible combination. At Renault, he beat Ferrari and Schumacher to the title in 2005 and 2006 and will be many people's favourite to add a third crown.
Ominously, the Spaniard said last month the Ferrari F10 was the best car he has driven and the team were hiding their true potential.
Massa is returning from the life-threatening head injury he suffered in Hungary last July and is determined to show he is as competitive as ever.
Ferrari have been working on this car intensively since mid-2009 and have looked very quick in testing.
Image: Fernando Alonso
Fresh beginning for Sauber
The car, designed before former owners BMW quit the scene, has looked competitive in testing although pre-season appearances can be deceptive.
Budget and resources could be a problem but the pairing of drivers looks solid. Pedro de la Rosa is a veteran with years of experience as McLaren's tester, while rookie Kamui Kobayashi won plenty of admirers with his performance as a stand-in for Toyota at the end of last year.
Should be mid-table, but the podium may be out of reach.
Image: Pedro de la Rosa and Kamui Kobayashi unveil the new car
Williams will bank on Barrichello
The former world champions have not won a race since 2004 and will need everything to fall into place if they are to break out of the midfield this year.
Rubens Barrichello brings plenty of experience as a race winner, which will help highly-rated rookie Nico Hulkenberg who has had an impressive few months in testing.
A question mark hangs over the Cosworth engine, although the last pre-season test in Barcelona went well.
Image: Ruben Barrichello
Renault look to rise from ashes
Much has changed since the days when Renault were the team to beat. The car has lacked grip in testing but the team should have improvements for Bahrain.
Luxembourg-based businessman Gerard Lopez is now calling the shots, while Eric Boullier has taken over as principal in the post-Flavio Briatore era.
Robert Kubica is the prize asset, a talented and determined driver who will push the team hard. Vitaly Petrov is Russia's first F1 driver but faces a steep learning curve.
Renault are racing under a suspended permanent ban after last year's race-fixing furore.
Image: Robert Kubica
Mallya's hopes rest on Sutil
Force India showed last season that they are up-and-coming, taking their first pole, points and podium finish.
The Mercedes engine is strong and the cooperation agreement with McLaren is also an advantage. Despite owner Vijay Mallya's millions, budgets remain tight.
Vitantonio Liuzzi is quick and eager to show he deserves his place while Adrian Sutil is approaching a watershed after staying on for a fourth successive season. He needs to deliver solid results. The car has looked consistent in testing.
Image: Force India drivers at the launch of the car
New beginning for Toro Rosso
Ferrari-powered and running their own car after previously sharing designs with sister team Red Bull.
The extraordinary high of winning at Monza in 2008 has gone and Toro Rosso struggled last season. There is nothing to suggest this year will be much different, although Jaime Alguersuari, who turns 20 this month, at least knows most of the circuits now.
Sebastian Buemi, still only 21, is almost an older statesman in comparison.
Image: Sebastian Buemi
Miles to go fro Lotus F1
The Malaysian-backed team could turn out to be the best of the newcomers, reviving one of the sport's greatest and most successful marques after a 16-year absence, but they still look miles off the pace.
They were five seconds slower than McLaren in Barcelona. Technical head Mike Gascoyne is an astute and fierce competitor who has been around the block a few times and both drivers are past winners with plenty of experience.
A new aero package due by May should help to narrow the gap.
Image: Heikki Kovalainen
Can't expect much from them
Has one of the smallest budgets in the sport and a car designed exclusively on computers rather than in wind tunnels.
Pre-season testing has been problematic, particularly with the hydraulic system, and the car has been more than five seconds off the pace.
Team boss John Booth is well-versed in the world of motorsport after working with drivers such as Hamilton and Kimi Raikkonen at his Manor F3 team.
Designer Nick Wirth is promising regular updates and is confident his strategy is the right one. There are plenty of doubters among his rivals.
Image: Timo Glock
Struggling to stay afloat
Just turning up in Bahrain will be a success for Campos, who have struggled to stay afloat.
The team, now run by former Spyker and Force India boss Colin Kolles, have not taken part in any pre-season tests due to a lack of finance.
Bruno Senna, nephew of late triple champion Ayrton, was a runner-up in the GP2 support series. Indian rookie Karun Chandhok could be his team-mate.
Image: Bruno Senna