During a 10-year period from 1st January 1977 to 31st December 1986, a temporal artery biopsy was performed in 2307 patients in the city of Göteborg. The biopsy revealed giant cell arteritis (GCA) in 284 (12.5%) of patients. The average annual incidence of biopsy-proven GCA was 6.7 per 100,000 inhabitants. For women and men it was 9.9 and 3.5 per 100,000 inhabitants, respectively. In individuals aged 50 years or older, the average incidence was 18.3 per 100,000 inhabitants, with values of 25 and 9.4 for women and men, respectively. The annual incidence rate increased significantly (P less than 0.01) for women, but not for men; this result was not explained by demographic changes in the population.