A double-blind group comparative trial comparing Opticrom with a matching placebo, over a four-week period, in seasonal allergic conjunctivitis is reported. Overall assessment of treatment benefit made at the end of the trial by the patients and the clinician showed a statistically significant difference in favour of Opticrom. Of the patients on Opticrom, eighteen (90%) said they improved while in the clinicians opinion, seventeen (85%) improved. Six patients using Opticrom and five using placebo complained of stinging of the eyes, while one patient using placebo complained of his eyes becoming bloodshot and watering.