Inheritance of thermosensitive genic male sterility (TGMS) in Norin PL12 and IR32364TGMS and their allelic relationship were studied from F1, F2 testcross (TC) and F3 generations of the crosses made with the two mutants and several fertile tester parents. F2, TC and F3 segregation behavior for pollen and spikelet fertility indicated that the TGMS trait in the two mutants was controlled by a single recessive gene. Allelic relationship studies indicated that TGMS genes of the two mutants were different. Since TGMS gene in Norin PL12 has been designated as tms 2 , the TGMS gene present in IR32364TGMS is tentatively designated as tms 3 (t) until allelic test is done with another TGMS gene (tms 1 ) reported from China in a line 5460S seeds of which were not available.