['We observed that a number of patients presenting to our clinic with diverticular fistulation were taking nicorandil for angina. Recognised side effects of nicorandil include gastrointestinal and genital ulceration. The aim of our study was to determine whether nicorandil is an aetiological agent in diverticular fistulation.', 'We conducted a case-control study of patients with diverticular disease related enteric fistulae. Two patient groups were identified: a study group of patients with diverticular fistulae, and a control group with uncomplicated diverticular disease. The proportion of patients who had ever used nicorandil was compared between the two groups.', 'A total of 153 case notes were analysed, 69 patients with fistulae and 84 control patients with uncomplicated diverticular disease. Female to male ratio in both groups was 2:1. The mean age was 71 years in the fistula group and 69 years in the control diverticular disease group (P = ns). Of those with colonic fistulae, 16% were taking nicorandil compared with 2% of the control group (odds ratio 7.8; 95% confidence interval 1.5-39.1; P = 0.008). There was no significant difference in rates of ischaemic heart disease between fistula and control groups.'] Is diverticular fistulation associated with nicorandil usage?