The effects of a new ASA-nitroderivative compound, NCX 4016 (ASA-NO2), on platelet TXA2 synthesis after single and repeated doses in the rat were investigated. Compared to ASA, cumulative doses of ASA-NO2 showed similar inhibitory effects on platelet TXA2 synthesis and significant increases in nitrite/nitrate plasma concentrations 1 h after the last drug administration: 24 h later nitrite/nitrate plasma levels returned to the control values, while serum TXA2 concentrations did not change. A time-course study after a single dose of ASA-NO2 showed a significant inhibition of platelet TXA2 production also 24 h after drug administration and a significant increase in nitrite/nitrate plasma levels until 10 h.