A polyphasic taxonomic study of 15 bovine and human strains assigned to the catalase-negative, urease-positive campylobacter (CNUPC) group identified these bacteria as a novel, ureolytic biovar of Campylobacter sputorum for which we propose the name C. sputorum bv. paraureolyticus: suitable reference strains are LMG 11764 (human isolate) and LMG 17590 (= CCUG 37579, bovine isolate). The present study confirmed previous findings showing that the salient biochemical tests used to differentiate C. sputorum bv. sputorum from C. sputorum bv. bubulus are not reproducible; and that the absolute validity of source-specific biovars of the species is questionable. A correlation between the results of numerical analysis of protein profiles and the reaction of strains in certain enzyme tests was, however, noted. Therefore, it is proposed that the infrasubspecific (biovar) divisions of C. sputorum should be revised to include bv. sputorum for catalase-negative strains; bv. fecalis for catalase-positive strains; and bv. paraureolyticus for urease-positive strains. Strains classified previously as bv. bubulus should be reclassified as bv. sputorum. The species description of C. sputorum is revised accordingly.