Nodulation mutants induced by EMS mutagenesis were available from two different germplasm sources of common bean (Phaseolus vulgaris L). They were the lines R32 (nitrate tolerant supernodulation, NTSN, nts gene), R69 (ineffective nodulation, IN, nie gene), and R99 (nonnodulation, NN, nnd-2 gene) originating from OAC Rico navy bean, and CIAT lines NOD125 (NN, sym-1 gene) and NOD238 (IN, sym-2 gene) from RIZ30 small red variegated bean. Crosses between the two mutant groups were made to determine genetic complementation of nodulation genes of the mutants. Nodulation of all F,s between the two sources were similar to that of the wild type, suggesting the presence of genetic complementation. The FjS revealed that both sym-2 and nie, and sym-1 and nnd-2 were epistatic to nts, and sym-1 and nnd-2 were epistatic to sym-2 and nie. The nie of R69 was epistatic to sym-2 of NOD238. Genes sym-2 and nie of NN between the two sources were nonallelic. A series of epistatic control of nodulation genes was discussed in context of progressive timing of nodulation ontogeny.