['To assess hematologic recovery and procedure-related mortality in patients who received high-dose therapy with stem-cell support, in whom the peripheral-blood stem-cell (PBSC) collection fails (CD34+ cells < 1 x 10(6)/kg). The predictive value of granulocyte-monocyte colony-forming cell (GM-CFC) measurements and the value of bone marrow obtained after PBSC collection failure was assessed.', 'The study group comprised 324 consecutive patients mobilized with granulocyte colony-stimulating factor (G-CSF) and cyclophosphamide (273 patients), G-CSF with other chemotherapy (37 patients), and G-CSF alone (14 patients). Between one and four aphereses were performed.', 'In 51 of 324 patients, there was failure to obtain 1 x 10(6)/kg CD34+ cells. Twenty-three patients had greater than 1 x 10(5)/kg GM-CFC; 22 patients proceeded to high-dose therapy. Neutrophil recovery occurred within 21 days, but platelet independence was delayed (> 28 days) in eight patients. Of 28 patients with less than 1 x 10(5)/kg GM-CFC, six received high-dose therapy with PBSC alone and five had delayed engraftment. Twelve patients with less than 1 x 10(5)/kg GM-CFC received high-dose therapy supported by bone marrow collected after PBSC collection failure. Eleven patients were assessable for engraftment; four patients had slow (> 21 days) or delayed (> 28 days) neutrophil recovery and eight patients had delayed platelet recovery. In the group of patients who received less than 1 x 10(5)/kg GM-CFC, there were five procedure-related deaths.'] Is back-up bone marrow frequently ineffective in patients with poor peripheral-blood stem-cell mobilization?