The presence or absence of the Fc receptor (FcR) on bone marrow lymphoblasts was evaluated in 279 cases of acute lymphoblastic leukemia (ALL) by member institutions of the Pediatric Oncology Group (POG). The case material was classified as follows: 19 cases of positive (greater than or equal to 20% +), 24 additional cases as intermediate (greater than or equal to 10% but less than 20%), and the remaining 236 cases as negative (less than 10%). Intermediate and positive cases were relatively equally distributed between null cell leukemia and pre-B-cell leukemia, and there were one intermediate and two positive T-cell cases. One of two cases of B-cell leukemia was also positive. There were no distinguishing clinical or laboratory characteristics which distinguished the FcR+ cases, nor was the FcR of prognostic significance within ALL as a group or within immunologically defined phenotypes.