Various dosages of the anticancer agent 1,3-bis(2-chloroethyl)-1-nitrosourea (carmustine, BCNU) were administered to 28 normal rabbit eyes. Single injections and series of injections were given to determine the tolerance and toxicity levels of this drug when injected directly into the vitreous cavity, the anterior chamber, or the subtenon-retrobulbar space. During a follow-up period of 3 weeks to 4 months, no significant ocular changes were noted following a single injection of BCNU into the vitreous (0.002–0.50 mg) or anterior chamber (0.001–0.250 mg), or 10 daily subtenon-retrobulbar injections (0.5–1.0mg each). When the daily dosage was increased to 1.5–2.0 mg, corneal damage with stromal infiltration, edema, and vascularization were found after the course of the 10 subtenon-retrobulbar injections in 3 of 6 test animals.