SummaryContrary to what would be expected from data in the literature, mutations in thefsoCgene of the F71(fso)P‐fimbrial gene cluster do not completely block fimbrial biogenesis.fsoCmutants still express small amounts of fimbriae of normal length, which carry the non‐adhesive minor subunit protein, FsoE, but lack the adhesin, FsoG. The FsoC protein operates at the same stage in fimbrial biogenesis as the FsoF and FsoG proteins. The data suggest that FsoC, FsoF and FsoG interact to form an initiation complex for fimbrial biogene