Eighty-eight patients who received single fraction total body irradiation (sfTBI) as part of their conditioning for allogeneic BMT have been evaluated for the risk of cataract formation. Thirty-eight (43%) have developed cataracts; 11 required surgery. With 9.5-13.6 years follow-up (median 10.7 years), all 12 recipients of unmanipulated marrow allografts have developed cataracts; the actuarial risk of needing surgery was 32 (+/- 18%, 95% confidence intervals (CI)). Ten of these 12 required high-dose steroids (prednisolone > 1 mg/kg/day) for the treatment of GVHD. Seventy-six patients received T cell-depleted allografts; 14 of 76 required post-transplant immunosuppression with high-dose steroids. With 1-9.4 years follow-up (median 5 years), the actuarial risk of cataract formation in T cell-depleted allograft recipients is 72% (+/- 52% CI), the actuarial risk for needing surgery is 20% (+/- 9% CI). Recipients of sfTBI and non-T cell-depleted allografts had a significantly greater risk of developing cataracts (p = 0.003, long rank test) and of needing surgery (p < 0.05, log rank test) than patients receiving T cell-depleted BM. Cataracts occurred more frequently in patients requiring post-transplant immunosuppression with steroids (relative risk 2.12, p < 0.01 log rank test).