The F2 populations and F3 progenies from 10 soybean [Glycine max] crosses were tested with physiologic races 1, 2, 3 and 4 of P. megasperma var. sojae. The soybean cultivars and plant introductions, ''Harosoy'' (susceptible to races 1, 2, 3 and 4), ''Mukden'' (resistant to races 1 and 2; susceptible to races 3 and 4), P.I. 54615-1 (resistant to races 1, 2 and 3; susceptible to race 4), P.I. 84637 (resistant to races 1, 3 and 4; susceptible to race 2), and P.I. 86972-1 (resistant to races 1, 2, 3 and 4) were selected as parents based on their reaction to the 4 races of the pathogen and each one was crossed to the other four. The resistance of ''Mukden'', P.I. 54615-1 and P.I. 84637 is controlled by a different single dominant allele in each located at the same locus. To differentiate these alleles it is suggested that the allele in P.I. 54615-1 be designated Rpsc and the allele in P.I. 84637 be changed from rps12 to Rpsb to form the allelomorphic series Rpsa, Rpsb, Rpsc and rps, represented by ''Mukden'', P.I. 84637, P.I. 54615-1 and ''Harosoy'', respectively. The resistance of P.I. 86972-1 is controlled by a single dominant allele located at different locus. It is suggested that this allele provisionally be designated Rps3.