A polymerase chain reaction method was developed for the specific detection of the botulinum neurotoxin (BoNT) gene of Clostridium botulinum. Degenerate oligonucleotide primers, designed from the nucleotide sequence of the heavy chain of the BoNT gene, amplified a specific fragment of approximately 1.1 kb from strains of C. botulinum toxin types A, B, E, F, and G and neurotoxin-producing strains of Clostridium barati and Clostridium butyricum, but no fragment was obtained from nontoxigenic strains. The fragments amplified from several strains of C. botulinum types B, E, and F were cloned in Escherichia coli and their nucleotide sequences were determined. Sequences within this region were used to design oligonucleotide probes specific for BoNT type B (BoNT/B), BoNT/E, and BoNT/F genes. An additional probe was designed for the detection of the BoNT/F gene of C. barati, which differed in sequence from BoNT/F genes of both proteolytic and nonproteolytic strains of C. botulinum.