The aim of this work was to study the evolution of neutrophil functions in non-neutropenic cancer patients. Thirty non-neutropenic patients, median age 35 years (range 19-52), with solid tumors (n = 21) or lymphomas (n = 9) entered a phase I study of five days of s.c. (n = 24) or i.v. bolus (n = 6) lenograstim, recombinant human glycosylated granulocyte colony-stimulating factor (rHuG-CSF Chugai-Rhône-Poulenc), with dose escalation from 1 to 40 micrograms/kg/day. Neutrophil functions were studied before lenograstim (D1) and 24 h after the last dose (D6). Granulocyte count rose in a significant way, and enzyme release, phagocytosis and bacterial killing were stimulated. All patients had improvement of at least one neutrophil function. Directed migration was depressed, although it was still in the normal range. These findings confirm that lenograstim is a potent activator of neutrophil functions in non-neutropenic cancer patients and may be useful as an adjunct to conventional antimicrobial therapy.