The Effect of Soil Solarization on Phytophtora nicotianae Breda de Haan var. parasitica (Dastur) G.M. Waterhouse Responsable for Syndrome Associating Root Rots and Damping-off of Pepper (Capsicum annuum L.) in Tunisia. Mycological analysis of soil collected from solarized plot and non solarized plot showed that the inoculum of soil is composed mainly by Fusarium spp. The solarization permitted to reduce the density of this inoculum. Isolations done from peppers wilted plants have revealed the infestation by Phytophtora nicotianae Breda de Haan var. parasitica (Dastur) G.M. Waterhouse. This was on the basis of microscopic observation of different structures. It is assumed that the percentage of wilted plant showed a considerable reduction in solarized plot. In the same time, the impact of the solarization on the agronomic criteria showed an improvement of the vigour and also of the yield.