Successful complete hematopoietic reconstitution (CHR) using nonleukemic peripheral stem cells (PSC) after marrow ablation has been reported in animals but not man. Previous studies of cytapheresis products from humans, as a prelude to use for CHR, have documented the presence of committed myeloid (CFU-GM) and erythroid (BFU-E) precursors. We have examined mononuclear cell (MNC) products collected on the Fenwal CS3000 Blood Cell Separator for these plus the more primitive mixed (granulo-, erythro-, mono-, and megakaryocytic) cell colony-forming units (CFU-GEMM) and for various lymphocytic subpopulations (LSP). One to two-hour products contained 36 +/- 7 CFU- GEMM/10(6) MNC (mean +/- SE, n = 8) or 490 +/- 131/ml product. This compared favorably with blood (23 +/- .4/10(6) MNC or 46 +/- 8/ml, n = 14) and bone marrow (146 +/- 58/10(6) MNC, n = 12). Collection efficiency for E-rosette-positive cells approximated that for total lymphocytes and was variable for other LSP. Recovery of CFU-GEMM after freezing in 10% dimethylsulfoxide at a controlled rate and storage in liquid N2 was 54% +/- 8% (n = 8). Cytapheresis collection of large numbers of pluripotent hematopoietic precursors and demonstration of adequate recovery of these after cryopreservation, both previously unreported, are significant steps toward eventual CHR using nonleukemic PSC.