Although Behcet's disease is mainly diagnosed during the reproductive periods of life, we know little about the influence of pregnancy on the clinical course of Behcet's disease. Therefore, we analyzed the relationship between Behcet's disease and pregnancy retrospectively, in order to detect any possible interaction between the two multisystemic processes, particularly in regard to the influence of pregnancy on the clinical course of Behcet's disease. We studied 44 pregnancies in 28 women with Behcet's disease. The diagnoses were made according to the criteria of the International Study Group for Behcet's disease. The patients were observed during pregnancy and puerperium periods at monthly intervals. The existence and incidence of symptoms were recorded during these periods. There was remission of Behcet's disease during 23 (52.3%) pregnancies, although the disease had been in a stage of exacerbation before pregnancy. The disease became exacerbated during 12 (27.3%) pregnancies, although it had been in a stage of remission before pregnancy. There were no changes in the clinical course of Behcet's disease in 9 (20.4%) pregnancies. The most frequent manifestations of the clinical exacerbation were increases in the intensity and severity of outbreaks of oral ulcers during pregnancy. Outbreaks of genital ulcers, eye inflammations, and arthritis were other signs of exacerbation. Other than spontaneous abortion in three patients, we did not observe maternal or fetal complications. Although Behcet's disease tends toward remission during pregnancy, the influence of pregnancy on its clinical course is quite variable between patients and even during different pregnancies in the same patient. On the basis of our and previous results, we speculate that pregnancy in general does not seem to markedly affect the natural course of Behcet's disease.