To assess the efficacy and safety of twice-daily administration of nedocromil sodium 2% ophthalmic solution, we performed a multicenter study involving 140 patients with seasonal allergic conjunctivitis. Subjects had a history of seasonal allergic conjunctivitis and positive results of a skin test to ragweed. The trial coincided with the peak ragweed pollen season at five treatment centers. Patients treated with nedocromil sodium had improvements in symptoms with statistically significant reductions recorded for eye itching (P ≤ .04), conjunctival injection (P ≤ .001), and overall disease severity (P ≤ .001) as compared to the placebo-treated group. Adverse events were minor and transient. We concluded that nedocromil sodium 2% ophthalmic solution administered twice daily is effective in relieving major symptoms associated with seasonal allergic conjunctivitis.