A large, single-source Salmonella outbreak caused by a rare serovar Bovismorbificans (6,8:r:1,5) occurred in southern Finland in 1994. The origin of the outbreak was sprouted alfalfa seeds. A questionnaire was mailed to all 210 subjects with positive stool culture. Ninety-one percent (191/210) returned the questionnaire. One hundred and fifty-three (80%) were adults. One hundred and fifty-nine out of one hundred and ninety-one (83%) reported diarrhoea, 109 (57%) fever, 104 (54%) abdominal pains, 83 (43%) fatigue, 66 (35%) articular symptoms and 20 (10%) had no symptoms. The median duration of diarrhoea was 5 days (range 1-35), that of other symptoms 4 days (range 1-30). Those reporting articular symptoms were examined (51 patients) or contacted by telephone (13 patients). Twelve percent (22/191) fulfilled the criteria for reactive arthritis (ReA). The difference in the incidence of ReA between children and adults was not significant (8%, vs. 12%). The median onset of joint symptoms was 8.5 days; symptoms were oligoarticular in 14 (67%) and polyarticular in four (19%) patients. Mostly ReA was mild, but in four patients (18%) the joint symptoms lasted for more than 4 months. Ten (45%) ReA patients had HLA-B27 tissue type. The duration and severity of ReA did not differ between HLA-B27 positive and negative patients. Fourteen (64%) ReA patients had received fluoroquinolone treatment before reactive joint or tendon symptoms manifested, but this treatment did not prevent ReA symptoms.