Genetic engineering is an important tool which can be used together with conventional breeding methods in transferring certain economically important traits into cultivated varieties of almost any crop species. One of the methods for gene transfer is the particle bombardment technique. Several primary explants can be used with this technique for the transformation of groundnut. This study explored the use of mature embryo axes as explants for somatic embryogenesis, and determined the effect of medium composition on four South African genotypes. A modified Murashige and Skoog-medium was used with various concentrations of picloram. Mature embryo axes were found to be a suitable explant for induction of somatic embryogenesis. A significant difference was found in the response of the different genotypes to medium composition.