In each of the five years 1978 to 1982, seed lots of cv. Bintje, variously infested by Phoma foveata Foister and Fusarium solani var. coeruleum (Sacc.) Booth, as found by wound and cut tests, respectively, were planted in a series of field experiments at six sites in Sweden. A statistically significant relationship between seed and progeny infestation was found for P. foveata each year, and in three years for F. solani. Benomyl and thiabendazole mist treatments of seed tubers at grading in spring controlled the development of gangrene and dry rot in treated seed tubers, but did not consistently reduce the levels of P. foveata and F. solani infestation in progeny from treated seed tubers. The site of cultivation markedly influenced mean levels of P. foveata infestation, which were found to be related to temperature and rainfall during a 40 day pre-harvest period at the trial sites; however, mean levels of F. solani infestation were not so related.