Abstract: Resistance to early blight (EB) disease of tomato caused by Alternaria solani was assessed by examining various parameters of the disease progress. For this study twenty three diverse tomato genotypes were screened under replicated trials for over three years (2007-2009) using artificial inoculation under controlled conditions as well as under natural epidemics at Indian Institute of Vegetable Research, Varanasi, UP, India. Tested genotypes showed significant difference in their response to A. solani and disease severity. Area under disease progress curve (AUPDC) was positively correlated with percent disease index (PDI) and negatively with resistance. Of the 23 genotypes, only two i.e. EC-520061 (Solanum habrochaites) and H-88-78-1 (S. lycopersicum) were highly resistant (PDI < 5.0; AUDPC < 200 and r value > 0.12) for EB disease under field and glasshouse environments. Characterization using molecular markers also indicated their resistance. It was concluded that there are significant differences between resistant and susceptible tomato lines against EB disease and some of the lines should be considered resistant rather than tolerant. Hence, the choice of resistant lines can be utilized in future breeding programmes for development of early blight resistant/tolerant cultivars of tomato.