SUMMARY1.Studies were made of 14 cultures ofColletotrichum destructivumwith respect to the loss of sporulation.2.Variant types were isolated from sectors and patches in old cultures which differed from the original in various cultural characters. Some produced very few spores while others produced many more spores than the original cultures from which they came.3.The original cultures retained their ability to sporulate through 10 successive single spore generations. Transfers to sterile host tissue and to the living host did not cause poorly sporulating cultures to regain their ability to sporulate heavily.4.Two variants were obtained from lesions on red clover seedlings produced under sterile conditions.5.Conidia were predominantly uni-nucleate, a few being found which were bi-nucleate.6.It is concluded that the loss of sporulation in cultures was due to the occurrence of poorly sporulating types genetically different from the original type which they replaced.