The Association Internationale des Automobile Clubs Reconnus introduced a maximum dry weight limit of 750 kg, intended to curb escalating speeds by discouraging large-displacement engines. The incumbent constructors — Alfa Romeo, Maserati, and Bugatti — had cars already close to the permitted weight and adapted their existing models. Alfa Romeo's Tipo B (P3) received an uprated 2.9-litre engine and remained the car to beat among the Italian manufacturers.
The decisive factor was the arrival of two state-sponsored German teams. Mercedes-Benz introduced the W25, a supercharged straight-eight of 3.36 litres developing around 350 bhp, designed by Hans Nibel and described in a press release as a "silvery arrow." Auto Union unveiled the radical Type A (P-Wagen), conceived by Ferdinand Porsche, placing a supercharged V16 mid-mounted behind the driver — an almost unheard-of configuration at the time — producing around 295 bhp that grew to 375 bhp by season's end. Both cars used fully independent suspension on all four wheels, in sharp contrast to the rigid-axle designs of their rivals. Both teams were allocated RM 450,000 each in government subsidies, with additional bonuses for podium finishes.
The season opened at Monaco without the German teams, who reserved their debut for their home race. Scuderia Ferrari ran the Tipo Bs, and it was the young Franco-Algerian Guy Moll — a recent Ferrari signing — who won the Monaco Grand Prix after team leader Louis Chiron hit the barriers while leading with two laps remaining. Ferrari continued dominant in the non-German races through North Africa, with victories at Tripoli, Casablanca, and Targa Florio.
The German teams made their public debut at the Avusrennen in Berlin before 220,000 spectators. Mercedes withdrew during practice citing fuel-pump problems, leaving Auto Union to run. Hans Stuck initially led before retiring, and Moll won for Ferrari in the specially streamlined Alfa Romeo, demonstrating the German cars were fast but unreliable. Mercedes opened its victory account a week later at the Eifelrennen at the Nürburgring, where Manfred von Brauchitsch took the win after Luigi Fagioli was controversially ordered to hold station behind a German driver.
The French Grand Prix at Montlhéry saw the German teams engage directly with Ferrari for the first time. The Auto Unions proved blisteringly fast in practice but suffered mechanical failures in the race. Ferrari dominated with Chiron, Varzi, and Moll finishing first, second, and third — Alfa Romeo's last great display of superiority before the German cars found reliability.
At the German Grand Prix on the Nürburgring, Stuck delivered Auto Union's first victory after Caracciola's engine failed while leading. Mercedes responded with victories at the Coppa Acerbo in Pescara and at the Italian Grand Prix at Monza, where Fagioli prevailed in a race of gruelling attrition.
A shadow fell over the Coppa Acerbo when Moll, closing on the lead while attempting to lap a slower car, lost control on the fast descent at Pescara and was killed after his car somersaulted. He was 23 years old.
The inaugural Swiss Grand Prix at the Bremgarten circuit near Bern saw Stuck lead from start to finish for Auto Union, with the race ending in further tragedy when Hugh Hamilton was killed after a puncture threw him into the pine trees. The Spanish Grand Prix at Lasarte gave Mercedes a dominant 1-2, while Auto Union won the Masaryk Grand Prix in Czechoslovakia in the final major event of the year.
Scuderia Ferrari, operating as Alfa Romeo's de facto works outfit, fielded Louis Chiron, Achille Varzi, and the late Guy Moll. Hans Stuck was Auto Union's standout performer, winning three major races. Mercedes relied on Rudolf Caracciola — still recovering from a serious accident and the death of his wife — alongside Fagioli and von Brauchitsch.
The voiturette class gained significant momentum during 1934, with English Racing Automobiles making their debut and young Englishman Richard Seaman emerging as a talent of note.
The 1934 season established a template for the following four years: German engineering and government investment outpacing Italian craftsmanship and French organisation. The Tipo B's days as a frontrunner were numbered. Hans Nibel died of a heart attack in November, to be replaced by Max Sailer, leaving Mercedes' technical direction in transition even as the team tightened its grip on grand prix racing. France remained a distant third force, Britain was still confined to the voiturette class, and the Scuderia Ferrari — despite its victories — understood the power balance had shifted decisively.