The distribution of the three alleles of the P adhesin gene papG (classes I-III) was assessed among 74 Escherichia coli urine isolates from women with first-episode or recurrent cystitis, and papG genotype was compared with clinical origin, O serogroup, agglutination of Gal(α1-4)Gal- coated latex beads and human or sheep erythrocytes, and hemolysin production. The class-III-only papG genotype (27% of strains) predominated over the I + III (3%) and II-only (7%) genotypes, irrespective of clinical category. In contrast to the class II papG allele, the class III allele was significantly concentrated in serogroups 06 and O18. Agglutination phenotypes corresponded significantly but incompletely with papG genotype, whereas hemolysin production and papG positivity were tightly correlated. These findings suggest that in acute cystitis in adult women, the class III papG allele predominates, confers distinctive agglutination phanotypes, and is restricted to specific E. coli lineages.