The genotoxic effects of the fungicide afugan were analysed by measuring chromosomal aberrations (CAs), sister chromatid exchange (SCE) and micronuclei (MN) in cultured human peripheral lymphocytes. Concentrations of 2.5, 5, 10 and 20 μg/ml of afugan were used during 24 and 48 h. Afugan significantly increased the frequency of CAs at 5, 10 and 20 μg/ml concentrations during a 48 h treatment period. A significant increase was observed for induction of SCE and MN at all treatments compared with the negative control. A significant dose-response correlation was found in all tests. Afugan did not affect the replicative index (RI), however it significantly decreased the mitotic index (MI) at all treatment concentrations except 2.5 μg/ml, and at both treatment times. The present results indicate that afugan is clastogenic and cytotoxic to cultured human lymphocytes. © 2006 Elsevier B.V. All rights reserved.