Thirty-two patients with keratoconjunctivitis sicca (KCS) were screened for the presence of antinuclear antibodies, rheumatoid factor, and autoantibodies associated with Sjögren's syndrome (designated SS-A and SS-B). None of these patients had or were found to have clinical evidence of connective-tissue disease. The conditions of 19 (59%) patients were antinuclear-antibody-positive and 18 (56%) were rheumatoid-factor-positive. We found SS-A and/or SS-B autoantibodies in ten (31%) patients. There seems to be a high incidence of serologic abnormalities in patients with KCS, even when those patients with connective-tissue disease are excluded. Serologic testing seems to be a useful adjunct in the early diagnosis of primary Sjögren's syndrome. The presence of SS-A and SS-B autoantibodies correlated well with the clinical diagnosis of Sjögren's syndrome and seemed to identify the conditions of patients who may have a higher incidence of systemic complications with KCS.