The prevoting conception of the incidence of giant cell arteritis (GCA) among population underscores the very low incidence of this disease among Jews. We studied the epidemiology, ethnic background, and seasonality of GCA among the Jewish population of Jerusalem. Eighty-four patients with biopsy-proven GCA were identified in a period of 12 yr, from 1980-1991. The age, sex and period-adjusted incidence of GCA was 10.2 per 100,000 population aged > or = 50 yr, approximately 20-fold higher than that reported for the Jewish population in Israel for the years 1960-1978. The female:male ratio was 1.6. A declining trend in the annual incidence was observed for men but not for women. The incidence rate was similar among non-western and western Jews. The onset of GCA was more common during the early summer months (May-June).