Champions Mercedes are chasing a sixth successive double, and Lewis Hamilton his sixth drivers' title, but the task looks tougher than ever.
Team-by-team prospects for the Formula One season starting in Melbourne on March 17, listed in 2018 championship order.
The racing numbers before the drivers' names are those they have chosen for the duration of their Grand Prix careers:
Lewis Hamilton (Britain), 77-Valtteri Bottas (Finland)
The champions are chasing a sixth successive double, and Hamilton his sixth drivers' title, but the task looks tougher than ever. Mercedes were slower than Ferrari in testing and their W10 car was less stable than their rivals' SF90. Reliability, error-free races and the relative pace of development will all be crucial but Hamilton can make the difference if the gap is close. Bottas will have to raise his game substantially from 2018 to keep his seat.
Likely outcome: Top two, maybe second this time.
Lewis Hamilton of Mercedes. Photograph: Dan Istitene/Getty Images
Sebastian Vettel (Germany), 16-Charles Leclerc (Monaco)
Ferrari start as early favourites. A changed lineup, with Leclerc joining after a season at Sauber and a new boss in long-time insider Mattia Binotto, has taken the team back to their racing roots and brought back a more open atmosphere. The car looked the pick of the field in testing but with some reliability niggles. Vettel is gunning for a fifth title, and should be the main focus but cannot afford any errors. Leclerc can hope to become Formula One's 108th race winner since 1950.
Likely outcome: First constructors' title since 2008.
IMAGE: Sebastian Vettel of Ferrari. Photograph: Dan Istitene/Getty Images
Max Verstappen (Netherlands), 10-Pierre Gasly (France)
Verstappen, 21, is now the effective team leader on track and a title contender as he starts his fifth season. Gasly, 23, has graduated from Toro Rosso to replace Australian Daniel Ricciardo. Wins could be on the cards for both but much will depend on the performance and reliability of the Honda engine, replacing Renault. The early indications are promising.
Likely outcome: Third again, closer to the top two.
IMAGE: Max Verstappen of Red Bull Racing. Photograph: Mark Thompson/Getty Images
3-Daniel Ricciardo (Australia), 27-Nico Hulkenberg (Germany)
Ricciardo arrives as a race winner and hungry for more while Hulkenberg, yet to stand on the podium, is out of contract at the end of the year and needs a strong campaign. Power and reliability will be key but Renault seem to have taken a step up on the engine side and have invested plenty of resources into getting closer to the top three. On the flip side, rivals also look quicker in a congested midfield.
Likely outcome: Fourth again, but it could be tight.
IMAGE: Daniel Ricciardo of Renault. Photograph: Charles Coates/Getty Images
8-Romain Grosjean (France), 20-Kevin Magnussen (Denmark)
Apart from Mercedes, Ferrari-powered Haas are the only team with an unchanged line-up. Experience counts but they need to use it and avoid mistakes. The midfield is looking far more competitive, with McLaren and Toro Rosso much improved in testing while Renault have a far bigger budget.
Likely outcome: Hanging on to fifth, maybe fourth.
IMAGE: Kevin Magnussen of Haas F1. Photograph: Dan Istitene/Getty Images
55-Carlos Sainz (Spain), 4-Lando Norris (Britain)
Norris, 19, is the youngest driver on the grid while Sainz, 24, is the face of experience in an all-new lineup replacing Spain's double world champion Fernando Alonso and Belgian Stoffel Vandoorne. The team got in plenty of laps in testing and the car also looked much improved compared to last year's.
Likely outcome: Challenging for fourth or fifth.
IMAGE: Lando Norris of Renault. Photograph: Charles Coates/Getty Images
11-Sergio Perez (Mexico), 18-Lance Stroll (Canada)
Perez remains from the old Force India days, Stroll joins a team that has consistently punched above its weight and is now owned by a consortium led by the Canadian's father Lawrence. The budget is there and the team have a spring in their step. Testing times suggest there is plenty of work to do, however, but a major upgrade is due before Melbourne.
Likely outcome: Could drop down the pecking order.
IMAGE: Lance Stroll of Racing Point. Photograph: Dan Istitene/Getty Images
7-Kimi Raikkonen (Finland), 99-Antonio Giovinazzi (Italy)
Raikkonen, who will be 40 this year, joins from Ferrari alongside Giovinazzi, who is starting his first full season, in an all-new lineup for the team previously known as Sauber. Close collaboration with Ferrari has paid dividends, the engine is good and the car has looked competitive in testing.
Likely outcome: Moving up in the world. Sixth in sight.
IMAGE: Antonio Giovinazzi of Alfa Romeo. Photograph: Charles Coates/Getty Images
26-Daniil Kvyat (Russia), 23-Alexander Albon (Thailand)
Another new lineup from 2018, although Kvyat has been here before. Both drivers have been dropped by Red Bull and then brought back, and both have something to prove. Albon, the first Thai driver since 1954, could be something of a revelation in his rookie season and won four races in F2 last year. More part sharing with Red Bull and an improved Honda engine will help.
Likely outcome: Also on the up, and also chasing sixth.
IMAGE: Alexander Albon of Toro Rosso. Photograph: Dan Istitne/Getty Images
88-Robert Kubica (Poland), 63-George Russell (Britain)
Mercedes-backed rookie Russell joins as reigning Formula Two champion and is a real talent. Kubica, 34, returns to the grid for the first time since 2010 in a stunning comeback from a near-fatal 2011 rally accident that partially severed his right forearm. On the downside, the car was slowest in testing after arriving late and still looks well off the pace even if it is handling better than 2018's unlamented model.
Likely outcome: On current form, last again.
IMAGE: George Russell of Williams. Photograph: Mark Thompson/Getty Images