Anti-inflammatory drugs, i.e. glucocorticosteroids and NSAIDs (nonsteroidal anti-inflammatory drugs), are often included in the treatment of allergic conjunctivitis. The present study compares the clinical efficacy and safety of topical hydrocortisone, acetylsalicylic acid (ASA) and piroxicam compared to placebo. The trial, designed as a double-blind, randomized and parallel-group treatment, was carried out in a group of 40 patients suffering from seasonal allergic conjunctivitis due to Parietaria pollen, during the pollen season (June-July, 1990). Patients received hydrocortisone 0.1% solution, ASA 1% solution, piroxicam 0.5% solution or placebo as eye drops, all one drop in each eye q.i.d. for 14 days. The symptoms were evaluated at baseline and at the end of treatment by the clinician and by patients on a diary card. The hydrocortisone group showed a rapid and significant improvement during the first week of treatment, while ASA and piroxicam reduced symptomatology during the second week of treatment; this difference was statistically significant. At the end of the trial, the active drugs were comparable with regard to clinical efficacy. A statistically significant difference was observed between the active drugs and placebo, while no statistically significant difference was observed among the three drugs. No serious side-effects were observed. The results demonstrate the clinical efficacy of anti-inflammatory drugs in the treatment of pollen-induced allergic conjunctivitis; they also suggest the use of NSAIDs in long-term treatment, as their efficacy has been shown to be closely comparable to that of steroids, while avoiding the well-known side-effects of the latter in prolonged treatment.