Information on the safety of mobilization and collection of peripheral blood progenitor cells (PBPC) in patients with advanced coronary heart disease (CHD) is limited. We report herein our early experience with patients participating in a Phase I trial of injection of autologous CD 34(+) cells into threatened, ischemic myocardium for neovascularization and symptom relief in patients with chronic refractory myocardial ischemia. All patients had advanced inoperable CHD despite the best medical therapy. Granulocyte colony stimulating factor (G-CSF, 5 microg/kg/day) was administered subcutaneously for 5 days for mobilization of CD34(+) cells into the peripheral blood. PBPCs were collected in the outpatient apheresis suite on day 5. Nine patients from our institution were evaluable. Adverse effects of mobilization included: increase in frequency and/or intensity of angina in 8 patients (88.8%); bone pain in 7 patients (77.7%); headaches in 4 patients (44.4%); 2 patients (22%) were hospitalized. Collection phase toxicities included: tingling in 5 patients (55.5%) and angina in 3 patients (33%). All procedures were completed without new myocardial infarction, congestive heart failure, or death. The median peripheral blood CD34(+) cell count on day 5 of G-CSF was 21 cells/microl (range 10-40 cells/microl). A median of 1.65 x 10(6) CD34(+) cells/kg (range: 0.13-3.0 x 10(6)/kg) were harvested. We conclude that mobilization and collection of PBPC in patients with advanced CHD can be safely performed as an outpatient procedure. Apheresis professionals should be aware of the intensity and frequency of angina in this patient population.