From a press release issued by the FIM:

July 15, 2004

Road Racing World Championship Grand Prix
Anti-doping controls

Anti-doping controls were carried out at the Italian Grand Prix, held on the circuit of Mugello, on June 6 last.

All the samples tested showed the absence of any banned substances.

The riders controlled were : Valentino Rossi (ITA, MotoGP), Ruben Xaus (SPA, MotoGP), Max Biaggi (ITA, MotoGP), Manuel Poggiali (RSM, 250cc), Alfonso Nieto (SPA, 250cc), Sebastian Porto (ARG, 250cc).