Three minor components of type 1 fimbriae, FimF, FimG and FimH have been characterized. These proteins are integrated in the fimbrial structure; are responsible for the adhesive properties of the fimbriae but are not necessary for the production of fimbriae. Fimbriae were purified from different clones harbouring various combinations of the fimF, fimG and fimH genes in addition to the fimA gene. The FimF, FimG and FimH proteins were identified by two dimentional gel electrophoresis. They were found to have molecular weights of 18.0 kDa, 17.0 kDa and 30 kDa, respectively. The ratio of FimF, FimG and FimH components to the major subunit was less than 1:100. The fimH protein especially was present in very small quantities. Sera raised against fimbriae from two of the clones (HB101/pPKL5 and HB101/pPKL4) were found by immunoblotting to be specific respectively for the major structural protein only (FimA), and for all components.