We studied the proportions of Th1 and Th2 cells in peripheral blood of 15 patients with primary Sjögren's syndrome (p-SS), by using a procedure to enumerate the cells synthesizing cytokines such as INF-gamma or IL-4 in cytoplasm of CD4+ lymphocytes. The frequency of Th1 (INF-gamma containing) cells in p-SS patients was significantly reduced as compared to normal control (20.57+/-7.48% vs 28.78+/-11.56%, p < 0.05), while that of Th2 (IL-4 containing) cells was not different from normal control (3.33+/-0.98% vs 2.85+/-1.88%). The ratio of Th1 to Th2 cells in p-SS patients was significantly decreased as compared to normal control (6.60+/-3.15 vs 11.55+/-6.72, p < 0.05). There was no difference in frequency of Th1 or of Th2 cells between 8 patients given small amounts of prednisolone (PSL) and 7 patients not given PSL (21.44+/-9.39% vs 19.57+/-5.05%, 3.12+/-0.80% vs 3.56+/-1.17%). The percentage of Th1 cells was not different between 7 patients with glandular symptoms (G) and 8 patients with extraglandular symptoms (EG) (18.61+/-9.63% vs 22.27+/-5.02%). Although the frequency of Th2 cells was higher in EG-patients than that in G-patients (3.84+/-0.78% vs 2.74+/-0.86%) with tendency of elevated IgG level in sera, the ratio of Th1 to Th2 cells was not different among them (6.26+/-2.84 vs 6.99+/-3.64). These results suggest that the reduced ratio of Th1 to Th2 cells is essential and is related to the dysfunction of cellular immunity in p-SS.