Three isoenzyme systems (amylase, esterase and glutamate oxaloacetate transaminase) were examined in seeds of pea (Pisum sativum L.) and shown to give clear variation in their band patterns on gel electrophoresis between different lines. The inheritance of these isoenzyme systems, and the location of their genes on the pea genome was investigated. Reciprocal crosses were made between lines, F2 seeds were analysed for segregation in the band patterns of the isoenzymes, and F2 plants were investigated to find linkage between the genes for these isoenzymes and genes for selected morphological markers. The results obtained showed that each of the investigated isoenzyme systems is genetically controlled by co-dominant alleles at a single locus. The gene for amylase was found to be on chromosome 2, linked to the loci k and wb (wb ... 9 ... k ... 25 ... Amy). The gene for esterase was found to be linked with the gene Br (chromosome 4) but the exact location is uncertain because of the lack of the morphological markers involved in the cross. The gene for glutamate oxaloacetate transaminase was found to be on chromosome 1 and linked with the loci a and d (a... 24... Got... 41 ... d).