Elimination of tumor cells from hematopoietic stem cell products is a major goal of bone marow-suported high-dose cancer chemotherapy. In patients (pts) with low-grade lymphoma Gianni et al (2000) assessed the ability of Rituximab, given in combination with high-dose chemotherapy, to eradicate PCR-detectable disease and enable the harvesting of large amounts of uncontaminated circulating progenitor cells. Our study was conducted in 27 consecutive pts with untreated bcl2 positive NHL (follicular lymphoma--7, chronic lymphocytic leukemia--13 and NHL in leukemic phase--7), 14 pts received Rituximab. Patients received 4 courses of standard-dose chemotherapy (CHOP or FLU-CY), followed by one course of high-dose cyclophosphamid plus G-CSF. Patients allocated to Rituximab received i.v. infusions of 375 mg/m2 48 hours before stem cell collection and in 3 weekly doses after transplantation (R-CHT). Clinical response after transplantation was evaluated in 26 pts who completed the treatment. The complete response rate was in 100% in the Rituximab group (PCR negative in 79%) versus 50% of controls (p<0.01). Yield of purged CD34+ cells was with median 5.23x10(6)/kg in CHT and 8.76x10(6)/kg in R-CHT pts. Toxicity in the both arms was acceptated (no difference). No significant difference was observed between CHT and R-CHT group in the mean number of days spent with neutropenia and trombocytopenia. After a follow-up of 31 months, no patient relapsed. Aside from providing PCR-negative harvests, the chemoimmunotherapy treatment produced complete clinical (100%) and molecular remission in 79% of evaluable pts. We showed that Rituximab in combination with effective high-dose anti- lymphoma chemotherapy, allowed the harvesting of large amounts of tumor free progenitor cells in evaluable pts.