Four-hundred-and-fifty-six patients with ulcerative colitis (UC) and 137 patients with Crohn's disease (CD) attended public hospitals within Auckland between 1969 and 1978. Polynesians comprised 15% of the population at risk but accounted for only 0.4% of UC cases and no CD cases. Annual incidence rates were 5.4/100,000 Caucasians for UC and 1.75 for CD. CD was significantly less common in Auckland than in European and North American centres. For patients presenting for the first time between 1969 and 1978, the cumulative probability of surviving 10 years was 93.9% for UC and 89.1% for CD. An excess of observed over expected mortality was limited to the first year of observation in UC and did not occur in CD. Clinical features and local complications of UC and CD have been correlated with the anatomic location of disease. In this first clinical study of inflammatory bowel disease of New Zealand, 61% of CD and 23% of UC patients required at least one surgical resection.