Glucocorticosteroids are often included in the treatment of allergic conjunctivitis. The present study compares the efficacy on clinical and cytological parameters and safety of topical clobetasone butyrate compared to placebo. The trial, designed as double blind, randomized and parallel group treatment, was carried out in 30 patients, suffering from seasonal allergic conjunctivitis due to Grass pollen, during the pollen season (June 1992). Patients received clobetasone butyrate 0.1% eye drops or placebo eye drops, two drops each eye, t.i.d. for 10 days. The clinical and cytological evidences were investigated on admission and at the end of treatment by clinicians and by patients on a dairy card. The steroid group showed a rapid and significant clinical improvement and at the end of the trial a statistically significant difference was evidenced between the active drug treated group and placebo treated group. No serious side effects were observed. The results show the clinical efficacy of clobetasone butyrate in the treatment of pollen-induced allergic conjunctivitis.