A case of acute lymphoblastic leukemia (ALL) cytogenetically characterized by trisomy 8 as a sole aberration is described. The patient, one of 116 adults with ALL investigated cytogenetically, was a 36-year-old male with leukocyte count 12.3 x 10(9)/liter with 90% blasts of FAB type L1 and common ALL immunological phenotype. Remission was achieved with the current U.K. treatment trial. The patient recovered from an autologous bone marrow transplant (BMT) in first remission but relapsed 15 months later. BMT, in second remission, from an unrelated donor, was rejected. Autologous reinfusion failed and he died 26 months after diagnosis. Molecular investigation of immunoglobulin gene rearrangement identified the same B cell clone at diagnosis and in relapse. The clinical and cytogenetic findings of six published cases of ALL with trisomy 8 have been reviewed with updates supplied by the authors. These reveal an heterogeneous group of patients ranging in age from 9 months to 39 years with no apparent association with a particular immunophenotype. Four patients were alive after 10-108 months follow-up. Two patients died, in relapse, 7 and 17 months after diagnosis. Thus trisomy 8 occurs in ALL with an incidence of 1-2%. The prognostic significance of this remains to be determined.