Degree of Ph-positive cell contamination of the graft predicts cytogenetic response 3 weeks, but not 3 months, after transplantation. Marrow or PB inoculum and BM obtained 3 weeks and 3 months after autografting was examined by metaphase analysis or FISH to determine the number of Ph-positive cells present. The number of Ph-positive cells found in the inoculum was then correlated with the number of Ph-positive cells present in BM after transplantation. A good correlation is observed between the cytogenetic response in the inoculum and at 3 weeks after transplantation. However, no correlation is observed between the cytogenetic response in the inoculum and 3 months after transplantation.