The fungicide methyl thiophanate (MT), widely used to control some of the most common fungal diseases in crops, is metabolized in animals into benzimidazole compounds, including the well-known reproductive toxicant carbendazim. However, standard toxicological tests did not indicate that MT may cause testicular toxicity and/or embryotoxicity, which are typical effects of many benzimidazoles. In the present study some aspects of the MT potential for reproductive toxicity have been assayed by means of two non-conventional models. Following the oral administration of 700 and 1000 mg kg(-1) body wt. for five consecutive days, short-term testicular toxicity was examined in the B6C3F1 mouse through specific parameters (sperm head count, specific enzyme activities, histopathology on days 3-35 post-dosing). In spite of the high doses administered, none of the testicular parameters examined, including histopathology, showed significant alterations as compared to controls at any time post-dosing. Pregnant CD rat dams were administered orally the limit dose of 650 mg kg(-1) body wt. day(-1) during preimplantation (gestational day or GD 2-5) or peri-implantation (GD 6-9) phases; embryos and adnexa were evaluated morphologically on GD 12 as a window for the early observation of embryotoxicity. Evident maternal toxicity was present in both treated groups, whereas only marginal reductions of the growth of embryos and adnexa were observed. A full understanding of MT toxicology will need more quantitative data on metabolism, including plasma kinetics and dosimetry of carbendazim at the relevant targets. Nevertheless, the absence of any clear-cut effect on a number of specific endpoints may provide reassurance that no further testing of MT is needed with regard to testicular toxicity or embryotoxicity.