In Egypt, no commercial tomato (Lycopersicon esculentum Mill.) varieties are available which are resistant to the late blight, one of the most important tomato diseases, caused by the phytopathogenic oomycete Phytophthora infestans. The wild tomato (Lycopersicon pimpenellifolium) shows resistance to P. infestans. So, in this investigation an interspecific cross between L.esculentum cv. Castle Rock and L. pimpenellifolium accession L3708 from the AVRDC were made. The genitors, F1, F2, BC1 and BC2 were used to study the inheritance of resistance to P. infestans and to estimate the genetic parameters associated with resistance. The resistance to P. infestans is controlled polygenic ally. The analysis of variances and genetic parameters suggested that this type of resistance was inherited quantitatively, and dominance was predominant over susceptibility, and not for resistance, that would be more interesting. The data supported the hypothesis that race-non-specific resistance in L. pimpenellifoliumL3708 is controlled by partially-dominant and dominant epistatic effects. The heritability in broad (Hb.s%) and narrow sense (Hn.s %) estimates were 73.28 and 26.86% for severity revealed the magnitude of the environmental factors on the total variation. The dominance gene effects were quire important in the inheritance of resistance to P. infestans. Estimates of additive gene effects were of low, magnitude. Epistatic gene effects were considered to be more important than the additive gene effects in the inheritance of resistance to P. infestans in the cross under study. The additive x additive, additive x dominance and dominance x dominance gene effects were highly significant. The reciprocal recurrent selection breeding is the best method to improve the resistance to P. infestans.