The role of the lom gene of bacteriophage lambda in adhesion of Escherichia coli to human buccal epithelial cells (HBC) was studied testing the adherence of lamda lom+ and lambda lom::TnphoA E. coli lysogens. lambda lom+ prophage increased 50% E. coli adhesion. This effect was not observed with lambda lom::TnphoA. These results suggest that the normal Lom protein participates directly in adhesion or regulates the synthesis of other protein(s), which may be involved in adhesion.