The present study was conducted at the Experimental Farm of Ismailia Agric. Res. Station during 2010 and 2011 summer seasons to estimate general and specific combining ability, heterosis, types of gene action for yield and its components, pod rot diseases and perharvest aflatoxin contamination in peanut. In the first season, five genotypes differed in their economic characters and tolerance to diseases were crossed in a diallel crosses(without reciprocal). In the second season, the five parents i.e   { P₁(line 85),P₂( line 367), P₃(line 284), P₄(line 205) and P₅(Giza 6)} and their ten crosses were field evaluated under artificial infection with fungi inocula i.e. Rhizoctonia solani the causal of dry brown lesion; Fusarium moniliforme the causal of pink discolorationas well as Macrophomina phaseolina and Sclerotium rolfsii the main causal pathogens of general breakdown pod rot, as well as  aflatoxigenic fungi i.e. Aspergillus flavus and A. parasiticus  in a randomized complete block design with three replications.  The most important results could be summarized as follows: -    F₁ mean values exceeded that of parents for all studied characters except plant height, number of branches and number of pods/plant. -    Specific combining ability had greater role than general combining ability for all the traits except 100-pod weight, 100-seed weight, shelling % and pod yield /fed. -    The first parent (line 85) was the best regarding general combining ability for 100-pod weight and 100-seed weight. The second parent (line 367) showed good general combining ability for most studied characters, the fifth parent ( Giza 6) had good general combining ability for the traits of 100-seed weight, shelling percentage, pod yield /fed and oil percentage.  -    The crosses (P₁ x P₂) and (P₃ x P₄) were superior in number of pods/plant, pod weight/plant, number of seeds/plant, seed weight/plant, shelling percentage and oil percentage, whereas, the crosses (P₁ x P₅ and P₂ x P₄) were superior in 100-pod weight and 100-seed weight, and the hybrid (P₁xP₄) was excellent in 100- pod weight and oil percentage . Positive and highly significant hetrotic effects relative to the better parent were found for most of the traits in the four crosses (P₁xP₂), (P₁xP₄ ),(P₂xP₄) and (P₃xP₄). Results indicated the importance of gene action due to dominance and additive effects for most characters. -The value of heritability was moderate to low in narrow sense but it was high in broad sense.   - Parents and F₁ differed in their sensitivity to pod rots under artificial infection in the field and their contamination with aflatoxin. -Crosses (P 1 x P 5) ,(P 2 x P 3) and Parental line 284 had the greatest resistance to all groups of pod rots followed by (P₃ x P₄) ,  (P₁ x P₄), (P₁ x P₃) and (P 2 x P 4). - Parental line 284 and crosses (P₁ x P ₃) , (P₁ x P₅),(P ₂ x P₃) and     (P₃ x P₄) were free of aflatoxin contamination ( B₁, B₂, G₁, G₂). Therefore, the superior of crosses   (P₁ x P₃)   , (P₁ x P₅) and (P₃ x P₄ ) in yield and its components, resistance to pod rot diseases and free of aflatoxin contamination, will be further evaluated in advanced experiments to develop new genotypes that have higher yield, disease resistance and free from aflatoxin contamination.