In a two year survey of Tunisian rustic potato stores, the losses were nearly equally distributed between dry rots induced by Fusarium solani and watery wound rot or leak caused by Pythium aphanidermatum and P. ultimum. Symptoms of leak were different from those normally induced by Pythium spp. Surveys of the growing potato crop confirmed the prevalence of these pathogens, which caused wilt and internal vascular stem necrosis. Most rotted progeny tubers also exhibited leak symptoms caused by P. aphanidermatum. Hardly any Erwinia diseases were found in Tunisia. The incidence of diseased plants was significantly higher in fields with successive cultivation of solanaceous crops, which may be attributed to a high rate of soil infestation by wilt-inducing pathogens such as Pythium spp., F. solani and Verticillium dahliae. The health of seed potatoes also played a significant role, affecting the incidence of rot in potato stores as well as in the soil before plant emergence. Therefore, Tunisian integrated management programmes for potato diseases should focus on soil disinfestation with appropriate crop rotation as well as seed quality and treatments. © 1999 Wiley. All rights reserved.