Purpose: To evaluate the feasibility of tacrolimus 0.03% dermatological ointment (Protopic) in the treatment of intractable allergic conjunctivitis. Methods: Twenty patients (mean age 10.8 years, range 6-26) with intractable allergic conjunctivitis were enrolled in an open-label study. Tacrolimus 0.03% ointment was applied into the conjunctival sac of both eyes twice daily for 8 weeks, followed by a 2-week washout period. Other ocular medications were discontinued. Conjunctivitis severity was recorded with a composite subjective/objective score (chemosis, tarsal papillary size, corneal staining, tearing, itching, and photophobia) at baseline, week 8, and after washout. Tacrolimus blood levels were measured at 2 weeks. Results: Statistically significant improvement in all categories of the conjunctivitis score was observed between baseline and the week 8 examination (p < 0.001). Adverse events were limited to local burning in one patient who discontinued treatment. Blood tacrolimus levels were mostly undetectable. Conclusions: Application of tacrolimus 0.03% dermatological ointment into the conjunctival sac appears to be effective, well tolerated, and safe in the treatment of allergic conjunctivitis refractory to traditional treatment.