Several antiaggregating agents were tested with regard to their effect on platelet malonylaldehyde (MDA) production which seems to be a good marker of prostaglandin metabolism. Non-steroidal antiinflammatory compounds, namely acetylsalicylic acid (ASA), ditazole and sulfinpyrazone, showed a sure, statistically significant, inhibitory effect on MDA production while theophylline, adenosine and alpha-blocking agent nycergoline did not. Dipyridamole on the contrary, was demonstrated to have a mild but still statistically significant effect on the inhibition of platelet MDA production.