We performed a controlled, randomized, double-masked, double-crossover clinical trial topically administered cromolyn sodium (4%) in 11 patientas with atopy and vernal keratoconjunctivitis. Statistically significant differences were noted in conjunctival injection, superifcial punctate keratitis, mucous production, and itching when eyes treated with cromolyn were compared to those treated with a placebo. The drug was well tolerated by all patients.