The polymerase chain reaction (PCR) procedure was evaluated to see if it is a simple and rapid method to detect Clostridium perfringens enterotoxin gene. The method, involving the use of two synthesised primers and gene amplification by the PCR procedure, detects a DNA fragment of 364 base pairs of C. perfringens enterotoxin gene by gel electrophoresis. The enterotoxin gene of strains was detected by use of purified chromosomal DNA. The supernatant of sporulating cultures in a sporulating medium was able to be used as template DNA. Template DNA can be obtained by merely culturing the strain in DS medium, a sporulating medium, for 48 h at 37 degrees C. All C. perfringens strains showing positive results in the PCR procedure were demonstrated to produce enterotoxin by a conventional method and all strains showing negative results were enterotoxin negative. To detect the enterotoxin gene in stool specimens by the PCR procedure, the specimen was heat-treated for 10 min at 90 degrees C and cultured in a sporulating medium, the supernatant of which was used as template DNA. From the stool specimens showing positive results in the PCR procedure by this method, enterotoxigenic C. perfringens was isolated from the heat-treated specimens. Thus, it is possible to detect enterotoxigenic C. perfringens in stools without isolation of the organism.