Intestines from 48 swine with enteric disease were examined by bacteriologic cultural technique for the presence of various Campylobacter species. Histopathologic techniques were used to determine whether the submitted specimens had lesions of either swine proliferative ileitis or other enteric diseases. Three species of Campylobacter were identified as Campylobacter jejuni/coli, Campylobacter sputorum ss mucosalis, and Campylobacter hyointestinalis (proposed new species) on the basis of biochemical characteristics and response to various inhibitory substances. The C hyointestinalis was isolated from 18 of 27 (67%) swine with proliferative ileitis and from only 1 of 21 (5%) swine with other enteric diseases. The C sputorum ss mucosalis was obtained from 16 of 27 (59%) swine with proliferative ileitis and from 2 of 21 (10%) swine with other enteric disease. The C jejuni/coli was isolated from 2 of 27 (7%) swine with proliferative ileitis and from 8 of 21 (38%) swine with other enteric disease. The new organism, C hyointestinalis, was catalase-positive, hydrogen sulfide positive in triple sugar iron agar, glycine tolerant, intolerant to 3.0% sodium chloride, able to grow at 25 C, sensitive to cephalothin, and resistant to nalidixic acid. On the basis of these characteristics, C hyointestinalis was differentiated from other campylobacters isolated from swine and from other sources.