Early blight (EB), caused by fungus Alternaria solani Sorauer, is a destructive disease of tomato (Lycopersicon esculentum Mill.) in Egypt and elsewhere. Sources of genetic resistance have been identified within tomato related wild species, so,  the resistance wild accession TL00970 from the AVRDC was crossed with three susceptible varieties (Castle Rock , Super marmande, Floradad) to produce three crosses (TL00970x castle rock ,TL00970 x Super Marmande and TL00970xFloradad ) . The genitors, F1, F2, BC1 and BC2 of the three crosses were used to study the inheritance of resistance Alternaria solani and to estimate the genetic parameters associated with resistance. Mean analysis, the F1 hybrids had severity at the end of epidemic values intermediary between those for the parents susceptible and the parent's resistant genitors the values were closer to the parent's susceptible genitors indicates that dominance was predominant over susceptibility, and not for resistance. Also, Mean analysis resulted in a more importance of the genic effect due to dominance, also, both additive, dominance and Epistatic (aa,ad, dd) effects were involved in early blight resistance  . The analysis of variance resulted in the estimated additive variance was more important than the variance due to dominance deviations. The estimates of heritability in broad and narrow sense were low, revealed the magnitude of the environmental factors on the total variation. The data revealed that early blight resistance was quantitatively controlled by more than one gene.