The 1929 Grand Prix season was another interim year, where most races were run to Formula Libre (open formula) rules due to a lack of regulations from the AIACR that would be popular for race organisers and manufacturers. This blurred the line between racing cars and sports cars with both competing in the same races. Bugatti won the major international races, with their drivers Louis Chiron and "W Williams". The Italian Championship proved very competitive, attracting many top drivers. There it was Alfa Romeo, using their 4-year old P2 model that claimed more victories, than their main competition coming from Bugatti and Maserati.
Chiron took a Delage across to Indianapolis but was outclassed by the Millers. Ray Keech won after duelling with the Millers of Lou Moore and Louis Meyer. Keech was killed a fortnight later at the AAA race at Altoona Speedway. Meyer went on to become the first back-to-back AAA champion.
The racing festival on the French Riviera held around Easter culminated in a new race – the Monaco Grand Prix. In a close race between Williams’ Bugatti and the Mercedes-Benz SSK sports car of Rudolf Caracciola, it was decided by a botched pit-stop for the German. The Targa Florio was another triumph for Bugatti, with Albert Divo claiming the fifth win in a row for the marque. Achille Varzi was the Italian Champion with victories at Alessandria, Rome, Montenero and Monza.