Three children, two girls and one boy, with Gaucher disease of the Norrbottnian type were treated by allogeneic bone marrow transplantation (BMT). Two of the donors were heterozygotes for Gaucher disease, and the third did not carry the gene. Engraftment was achieved in all three children but the boy became a chimera. The children have been followed from 1.5 to 6 years after transplantation. In each case the outcome was favourable, and in two children (patients 1 and 3) the BMT has been life saving. In all three cases a positive biochemical effect was apparent. Almost all biochemical parameters normalized within one year. The authors conclude that BMT is the treatment of choice in severe cases of Gaucher disease. BMT should be considered early in the course of disease and vigorous efforts made to find a suitable donor.