The prevalence of symptomatic secondary Sjögren's syndrome in 66 patients with SLE recruited from a defined population in southern Sweden was 59%. In 26 patients (39%) the symptoms were mild and variable, related to disease activity, while in a smaller group (20%) the symptoms appeared to be constant. The latter patients had an increased frequency of thyroid disease and autoantibodies to SS-A. The patients in this group were older, but did not seem to differ in regard to other disease manifestations.