There are varying reports on the prevalence of risk factors in porphyria cutanea tarda (PCT). We reviewed 84 patients with PCT in a restricted uptake area in Gothenburg, Sweden and evaluated different potential risk factors for the disease and complications. Besides a thorough medical history, the patients were investigated with urinary porphyrin analyses, transferrin saturation, ferritin and liver tests. Subsamples of patients were tested for antibodies to hepatitis C virus (n = 68), haemochromatosis gene mutations (n = 58) and with the oral glucose tolerance test (n = 31). We found a prevalence of about 1 patient with PCT in 10 000 inhabitants. Nineteen (23%) patients reported heredity for PCT. Identified risk factors were alcohol abuse (38% of male patients), oestrogen treatment (55% of female patients), anti-hepatitis C virus positivity (29% of male patients), diabetes (17%) or impaired glucose tolerance (45% of tested patients) and haemochromatosis gene mutations (57% of tested patients). All patients positive for anti-hepatitis C virus belonged to the non-hereditary group. During follow-up we observed a high incidence of stroke, no case of hepatocellular carcinoma and a normal life expectancy.