Following an outbreak of foodborne gastroenteritis caused by Salmonella typhimurium, questionnaires were sent to affected individuals and then to the family physicians of any who experienced extra‐enteric complications. Of 260 individuals infected with S typhimurium for whom adequate data were obtained, 19 patients developed joint disease (7.3%). All were men; the mean age ± SD was 39.3 ± 1.6 years. Among the 16 patients for whom this information was available, the interval from the onset of diarrhea to the onset of joint pain was <7 days in 7, 8–21 days in 2, and >21 days in 7. There was a significantly longer duration of diarrhea in those patients with joint disease (mean ± SEM 15.2 ± 2.6 days) than in those without complications (10.0 ± 1.1 days) (P < 0.01). The joint disease was monarticular in 3 patients and polyarticular in 16. The joints most commonly affected were the elbow (47%), wrist (47%), knee (42%), low back (32%), and shoulder (32%). Six of the 19 patients had at least 1 extraarticular feature: ocular (5 patients), mucosal (1 patient), urethral (2 patients), or cutaneous (1 patient). Of these 19 patients, 11 were located and agreed to HLA typing. Four were positive for HLA—B27, 6 were HLA—B7 positive, and 1 had HLA—Bw60. Of the 4 B27 positive patients, 3 were DR1 positive; of the 6 B7 positive patients, 5 were DR2 positive. A followup assessment 12.1 months after the acute infection revealed that of the 15 patients with arthritis (4 patients were lost to followup), 8 no longer had symptoms and 7 had persistent joint symptoms. Mucosal and urethral symptoms had resolved in all, and ocular symptoms had resolved in 90%. These findings highlight the interplay of microbe and major histocompatibility complex, a phenomenon that appears to be a precondition for the development of reactive arthritis.