A 22-year-old Spanish-American woman with juvenile rheumatoid arthritis developed anti-Cra after transfusion during colectomy. No Cra negative family members were found among 13 relatives, including four siblings and both parents. Chromium-labeled red cell survival studies showed a T1/2 of 14 days with Cra positive cells. Two units of Cra positive blood were transfused uneventfully for bleeding after ileorectal anastomosis.