Disodium cromoglycate (2%) (DSCG) was administered four times daily for one month to 10 patients using extended wear contact lenses. The same regimen was also followed for five days by 25 patients using daily wear soft contact lenses. The contact lenses and their soaking solutions were collected at the end of the wearing period and analyzed for DSCG, benzalkonium chloride (BAK), 2-phenylethanol, and EDTA. The lens soaking solutions and eluates prepared from the lenses were tested. In the extended wear group, small amounts of DSCG were detected in both the eluates and the soaking solutions. In the daily wear group DSCG was detected in small amounts in the soaking solutions but not in the eluates. BAK, EDTA, and 2-phenylethanol were not detected in any of the eluates or soaking solutions. During the study, no side effects of DSCG were observed in any of the patients. In animal experiments, radioactive DSCG was applied once to a series of rabbit eyes. Four hours after administration of the labelled DSCG, the animals' tears, cornea, and aqueous humor were examined for DSCG. Of the instilled dose, approximately 0.2% was found in the cornea, and less than 0.04% was found in the aqueous humor. We conclude that commercial DSCG applied topically to contact lenses does not result in the accumulation of either the drug or its preservatives in lenses and that DSCG can be safely applied directly onto a worn contact lens.