Fourteen isolates of E. coli O157:H7 and five isolates of S. dysenteriae type-1 were examined by polymerase chain reaction (PCR) for the structural genes (slt-I or slt-II), encoding Shiga-like toxins (SLTs). The two primer pairs (V1; 5'AGTTAATGTGGTGGCGAA and V2; 5'GACTGCGTCAGTGAGGTT for SLT-I, V3; 5'TTCGGTATCCTATTCCCG and V4; 5'TCT CTGGTCATTGTATTA for SLT-II) used were of the same positions representing the DNA sequence covering 471bp of the slt-I or slt-II. A 5-μl portion of boiled bacterial culture broth was used as template DNA in a PCR-reaction mixture of 50μl. Two classes, slt-I alone or both slt-I and slt-II, were recognized in E. coli strains. All of S. dysenteriae type-1 strains examined contained slt-I alone. Our results indicate that PCR using these primer pairs is a simple, rapid, sensitive, and specific method and suitable for use in routine diagnostic microbiology laboratories.