Chilli or Hot Pepper (Capsicum annuum var. annuum L.) is one of the most important economical and popular vegetable crops grown for its green fruits as vegetable and red form as spice. The present investigation was carried out to gather information on combining ability, gene action, genotype x environment interaction and magnitude of heterosis on different traits i.e. yield components, phenological , morphological, quality and disease resistance, by following 'line × tester' mating design. Significant genotype × environment interactions for all the characters indicated a definite role of environment on the performance of genotypes/crosses. The line × tester analysis revealed significant differences due to lines, testers and line × tester interaction for majority of the traits. The magnitude of non-additive gene action was predominant for majority of the traits with maximum contribution of lines in the expression of gene action. A wide variation in magnitude and direction of heterosis was noticed for majority of the traits. This book covers the genetical, breeding and disease resistance aspect of hot pepper breeding programme. It is quite beneficial for researchers and students.