A 19-kb DNA region containing genes involved in the biosynthesis of the capsule of Haemophilus influenzae serotype f (Hif) has been cloned and characterized. The Hif cap locus organization is typical of group II capsule biosynthetic loci found in other H. influenzae serotype b bacteria and other gram-negative bacteria. However, the Hif cap locus was not associated with an IS1016 element. Three new open reading frames, Fcs1, Fcs2, and Fcs3, were identified in the Hif capsule-specific region II. The chromosomal location of the Hif cap locus and the organization of the flanking sequences differed significantly from previously described division I H. influenzae serotypes.