Because of the importance of peanut (Arachis hypogaea L.) as an oil, food, and feed source worldwide and the contributions of breeding and genetics to yield and quality improvement, it is desirable to understand the genetic structure of the plant. Isozymes have been used to gain an understanding of the genetic structure of several plant species. However, we found no literature on the inheritance of isozymes in peanut. The F₁ and F₂ seed of several crosses between cultivars and plant introduction lines of three botantical types of peanut were used to investigate the inheritance of three isozymes by horizontal starch gel electrophoresis: phosphohexose isomerase (PHI), isocitrate dehydrogenase (IDH), and glutamate oxaloacetate transaminase (GOT). Each of the three enzymes displayed two different banding patterns, the difference being the presence vs. the absence of either one (IDH) or two (PHI, GOT) bands. Chi-square analysis for goodness of fit of the observed F₂ segregation ratios to ratios expected from genetic models indicated that the polymorphisms for both PHI and IDH are controlled by single genes. Two loci, Phi-1 and Idh-1, respectively, are proposed. Sixty-five of 71 F₁ progeny monitored for GOT showed the banding pattern of the male parent. The F₂ progeny segregated into the two parental types, but the ratios did not fit a simple genetic model. Possible explanations for the observed paternal inheritance of GOT include biparental transmission of plastids, prezygotic RNA synthesis and genomic imprinting.