From December 1999 to November 2001, a cluster of multi-drug-resistant Campylobacter jejuni subsp. jejuni enterocolitis was suspected within the male population of Montreal. Nine men, aged 26-40 years, presented with an erythromycin- and ciprofloxacin-resistant, tetracycline-susceptible C. jejuni enterocolitis. In March 1998 and February 2000, 2 additional men, aged 23 and 27 years, were infected with an erythromycin-resistant, ciprofloxacin and tetracycline-susceptible C. jejuni. All isolates were identical according to pulsed-field gel electrophoresis and flagellin typing. Epidemiological data suggested a sexually transmitted enteric infection; all patients infected with the locally acquired epidemic strain were men, the 8 patients for whom sexual orientation data were available identified themselves as men who have sex with men (MSM), and 3 of the patients had had a sexually transmitted Shigella sonnei infection during a proven outbreak among MSM. Eight patients, 6 of whom were identified as MSM, resided in a predominantly homosexual district of Montreal or its surrounding neighborhoods. The emergence of multidrug-resistant C. jejuni justifies routine susceptibility-testing of these bacteria. MSM should be educated about the prevention of sexually transmitted enteric pathogens.