The purpose of this study was to evaluate pre-transplant T-cell status in autologous hematopoietic progenitor-cell transplantation (HPCT) recipients. Between 1999 and 2002 we prospectively enrolled 85 autologous HPCT recipients with solid tumors (N = 50) or hematological malignancies (n = 35). Patient diagnoses included breast cancer (N = 49), non-Hodgkin's lymphoma (N = 20), myeloma (N = 11), Hodgkin's disease (N = 3), germ-cell tumor (N = 1) and amyloidosis (N = 1). Levels of CD3, CD4, CD8, memory and naïve CD4, and CD8 T-cell subsets were analyzed before autologous HPCT. Autologous HPCT recipients presented with lower pre-transplant counts of CD3, CD4, but not CD8 T cells, as compared to healthy controls. Pre-transplant CD4 T-cell levels correlated with progression-free survival (PFS) (P = 0.002) and overall survival (OS) (P = 0.05), in patients with hematologic malignancies (P = 0.02) and breast cancer (P = 0.04). Specifically, pre-transplant memory CD4 + CD45RA - CD62L - T-cell levels correlated with PFS (P = 0.01). The prognostic effects of pre-transplant CD4 and CD4 + CD45RA - CD62L - T cells were independent of tumor diagnosis, tumor stage, tumor sensitivity, and, for breast cancer patients, Her2 / neu status. Our results suggest that pre-transplant CD4 T-cell status, specifically CD4 + CD45RA - CD62L - memory T cells, correlates with the outcome of autologous HPCT recipients. These observations suggest the feasibility of prospective identification of those patients at higher risk of relapse, based on their immune status.