Strains of Escherichia coli isolated from cases of Sudden Infant Death Syndrome, healthy infants and infants that died of other causes were subjected to a series of tests with particular reference to serotyping, toxigenicity and adherence factors. E. coli from SIDS infants tended to have a low hydrophobicity and high toxigenicity, compared to those from healthy infants, while no notable differences in haemagglutination patterns were observed between these two groups of strains.