Experimental design for evaluating whether preceding exposure to pegylated, recombinant rat SCF enhances the hematologic effects of taxol, navelbine, vinblastine, or doxorubicin. SCF (50 mg/kg/injection) was administered to B6D2F1 mice subcutaneously every 12 hours for a total of three doses. Three hours before the last dose of SCF, a single intravenous injection of navelbine, vinblastine, or doxorubicin or an intraperitoneal dose of taxol, was administered. Dosages are described in Materials and Methods. Pairs of mice received either cytotoxic drug alone, SCF alone, SCF plus cytotoxic drug, or no treatment. The last dose of SCF was administered on the morning of day 1, and analysis was performed on day 3. Femurs and spleens were separately pooled for each experimental variable. Mononuclear cells (MNCs) were counted and plated in semisolid media. Colonies were scored on day 8 of culture, and the number of CFU-C per femur and spleen was calculated.