Carbonic anhydrase II (CAII) is expressed in oligodendrocytes, astrocytes and myelin in brains of rats and normal mice, but not in the brains of CAII-deficient mutant mice. We have transplanted mixed glial-cell suspensions from normal mouse brains, and oligodendrocyte-enriched precursor cells cultured from normal rat brains, respectively, into the brains of neonatal CAII-deficient mutant mice. Some CAII-positive astrocytes and oligodendrocytes developed in the brains of the host CAII-deficient mice at 8, 14 and 18 days posttransplant (DPT). In transplants of either mixed glial cells or oligodendrocyte precursors, CAII-positive oligodendrocytes were less plentiful than CAII-positive astrocytes and appeared to be less healthy. CAII-positive astrocytes developed by 8 DPT, and there were some oligodendrocytes in cerebral cortex at 14 DPT and in brainstem by 18 DPT. The data suggested that if glial-cell progenitors were to be injected into demyelinated lesions, any oligodendrocytes descended from the donor would be accompanied by astrocytes also descended from donor cells. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.