Nelson finished second while Prost and Senna were third and fourth ahead of Fabi with the final point going to Philippe Streiff in the Tyrrell-Ford/Cosworth. Prost went by later on the second lap and Piquet followed on the third lap. The Williams team had its new active-suspension system ready and Nelson Piquet used it, while Nigel Mansell stayed with a conventional car. I piloti, nel frattempo, spingevano per le dimissioni di Balestre.Nella riunione del 28 gennaio la FISA decise di multare di 10.000 Contro queste proposte si schierarono 5 membri del comitato esecutivo della FISA, tra cui Marco Piccinini, rappresentante dei costruttori automobilistici presenti in F1. But come the San Marino Grand Prix held at the fast Autodromo Dino Ferrari in Italy, Nelson Piquet had a huge accident at the flat out Tamburello corner when he suffered a tire failure during qualifying and was forbidden from racing by F1 doctor Sid Watkins. Non vi sono scarti. Mansell made a good start to lead Prost into the first corner but on the back straight Piquet blasted ahead of the McLaren to make it a Williams 1–2 with Prost third and Senna fourth ahead of the two Benettons, Boutsen ahead of Fabi. At the start of the second lap Berger challenged for second place and Mansell closed the door so the two cars collided and Boutsen moved to second place with Berger third and Mansell fourth. Prost was able to close up to Mansell and on lap seven the Frenchman went ahead. The top five did not change for the first half of the race with Senna at the front of a train of cars. Prost, appena rientrato in pista, fu vittima di una seconda foratura, che lo spinse all'ottavo posto della classifica, a un giro da Arnoux. Dit werd 2 jaar zo gedaan (tot en met 1984), waarna het weer voor 9 jaar verboden werd omwille van veiligheidsreden. Nelson Piquet's fortunate win in Hungary gave him a seven-point lead in the World Championship over Ayrton Senna with Nigel Mansell and Alain Prost 11 points behind Senna. Nelson Piquet was 18 points ahead with three races to go and so Nigel Mansell needed a good result without Piquet scoring too well. The pace of the Williams drivers and the superiority of the Williams FW11B on high-speed tracks meant that Mansell and Piquet lapped the entire field near the end of the race. Piquet had led for most of the afternoon but in the closing laps, with the home crowd roaring him on and having pitted for a fresh set of tires (Piquet had decided to go the entire distance on one set), Mansell closed up on Piquet and at Stowe Corner on lap 63 of 65 Mansell went ahead of his rival with a stunning passing maneuver. Third place went to Senna with fourth going to Satoru Nakajima in the second Lotus-Honda and the remaining points going to Derek Warwick (Arrows-Megatron/BMW) and Fabi. Then came Piquet and Teo Fabi (Benetton) with the top 10 completed by Ayrton Senna (Lotus), Riccardo Patrese (Brabham-BMW), Stefan Johansson's McLaren and the second Brabham of Andrea de Cesaris. The two Williams-Hondas were second and third with Boutsen behind them. Il nordirlandese proseguì nella rimonta superando anche Andretti e Cheever.
Piquet went into the lead but Mansell had a problem and was crawling away slowly. Then came Thierry Boutsen (Benetton-Ford), Alain Prost's McLaren-TAG, Michele Alboreto's Ferrari and Teo Fabi's Benetton. Goodyear decided that in the interests of safety it would fly in new tyres overnight for Saturday qualifying. Al giro 26 Giacomelli andò in testacoda alla curva Tre giri dopo Watson ebbe la meglio su Lauda e si avvicinò anche a Cheever, rallentato da Pironi. Tra il dodicesimo e il quattordicesimo passaggio andarono ai box sia Al diciannovesimo passaggio ci fu la svolta della gara: Piquet, giunto alla Al giro 37 Watson scontò la rottura di una sospensione all'Al giro 16 Arnoux si ritirò col motore fuori uso.