The possible clastogenic activity of Propineb, Propineb technical grade and of its main metabolite, propylene-thiourea (PLTU), was investigated by the micronucleus test in mice according to Schmid. No statistically significant increase in the percentage of micronuclei was observed at any of the tested doses of the above compounds. As positive controls, dose effect curves were constructed for methyl methanesulfonate (MMS) and mitomycin C (MMC).