Adult Nassarius reticulatus were exposed for two to three months to dissolved tributyltin (TBT), dibutyltin (DBT), triphenyltin (TPT) and diphenyltin (DPT) chlorides and to copper sulphate (CuSO4) in order to study the effectiveness of these compounds to induce imposex (penis and vas deferens development). The dialkyltins and copper did not promote imposex under exposure to 500 ng Sn l−1 and 500 ng Cu l−1. However, dissolved nominal concentrations varying between 100 and 500 ng Sn l−1 of TBT or TPT induced imposex in, respectively, 22 to 43% and 24 to 44% of the females. The testosterone titres of females increased significantly after two months' exposure to 250 ng Sn l−1 of TPT and TBT and the same happened to males exposed to 100 and 250 ng TPT-Sn l−1 and to 250 ng TBT-Sn l−1.