Oral and genital ulcerations have been previously reported in 3 Navajo children diagnosed with severe combined immunodeficiency disease with T- and B-cell lymphopenia (T-B(-)-SCID).To evaluate the occurrence of oral and genital ulcerations in 12 Athabascan-speaking American Indians with a diagnosis of T-B(-)-SCID (SCIDA group) and to compare their occurrence in non-Athabascan-speaking children with SCID (control group). We also observed the course of these ulcerations in response to bone marrow transplantation (BMT).Retrospective survey of the medical records of patients with SCID admitted from December 1, 1986, through July 31, 1995.Pediatric Bone Marrow Transplantation Division at a university hospital.Twelve children in the SCIDA group and 21 in the control group. All patients had virtual absence of T- and B-cell numbers and function at time of diagnosis.Oral and/or genital ulcers developed as a presenting feature of the SCIDA group. These ulcerations were not observed in the 21 controls. All patients underwent BMT. Of the 10 patients with oral and/or genital ulcerations, 3 had poor T-cell reconstitution after BMT, with recurrences of ulcers requiring additional BMTs.Oral and/or genital ulcerations are common in Athabascan-speaking American Indian children with T-B(-)-SCID but are not seen in non-Athabascan-speaking children with SCID. Thus, oral and/or genital ulceration appears to be an important, distinctive finding, and often a presenting feature of immunodeficiency in Athabascan-speaking American Indian children with SCID. Bone marrow transplantation with successful T-cell engraftment appears to be curative in the resolution of the ulcers, with recurrences only in patients who had poor T-cell reconstitution.