Soil solarization by mulching with polyethylene for 60 days during summer in Tunisia, was effective in reducing dramatically to a depth of 30 cm inoculum levels of Fusarium solani (Fs) from 3,000 to 450 propagules gram-1 of dry soil. Population densities of Pythium aphanidermatum (Pa) were reduced from 1,700 and 3,000 to 0.5 and 1 propagule gram-1 of dry soil in the top 15 cm and at 1-30 cm depth, respectively. After a subsequent autumn potato crop, populations of Pa remained very low in the previously solarized soil whereas propagule density in non-solarized soils was similar to the initial density. Also, inoculum level of Fs increased by 40% in nonsolarized soils while it remained unchanged in solarized soils, suggesting microbial processes that prevented soil reinfestation. All the annual weeds were eradicated by solar heating but not the perennial weed Convolvulus arvensis, Potato plant growth and yields were improved in solarized plots.