Objective. To assess the effect of azathioprine (AZA) treatment on long-term prognosis in Behçet's syndrome.

Methods. Patients (all male) who took part in a double-blind, placebo-controlled trial of AZA a mean ± SD of 94 ± 10 months previously were reevaluated.

Results. The emergence of blindness (log rank χ2 = 5.6, P = 0.02) and a 2-line drop in the visual acuity of the right eye (log rank χ2 = 5.9, P = 0.015) occurred significantly more frequently among the patients originally allocated to the placebo group compared with patients who originally received AZA, despite posttrial treatment for patients in both groups when needed. There was also a trend toward more frequent occurrence of extraocular complications in the placebo group. The beneficial effect of AZA was especially pronounced among patients who had eye involvement of short duration prior to their entry into the trial.

Conclusion. Early treatment with AZA tends to favorably affect the long-term prognosis of Behçet's syndrome.