Ergot pathogens of sorghum occurring in Japan were identified as Claviceps sorghicola and C. africana. C. sorghicola is the original fungus and it differs from the other Claviceps species infecting Sorghum in the color and texture of the sclerotia, morphology of stromata with clavicipitaceous stipes and capitula and the size of ascospores and conidia. It is predominant and widely distributed in Japan. C. africana is a pathogen with worldwide distribution which occurs mainly in the southern part of Japan. Host ranges of these fungi were restricted only to the genus Sorghum, based on the results of inoculation tests. Field tests showed that the method applied to sow the resistant sorghum lines at an earlier time was effective to avoid or control the occurrence of the ergot.