A randomized clinical trial was conducted to compare diclofenac sodium 0.1% ophthalmic solution to placebo in relieving ocular signs and symptoms in patients with acute seasonal allergic conjunctivitis. Twenty patients (10 per treatment) qualified for this two week, double-masked study with moderate itching, bulbar conjunctival injection and a positive skin test. Diclofenac was statistically and clinically superior in the physician's global evaluation (p = 0.03) and the primary composite score [itching + bulbar/palpebral conjunctival injection (p = 0.037)] after two weeks of treatment. Four patients experienced some transient ocular burning/stinging with diclofenac. Diclofenac sodium appears to be effective for relieving the ocular signs and symptoms associated with acute seasonal allergic conjunctivitis.