We enrolled 19 cancer patients (11 females, 8 males) with thrombocytopenia after standard dose of chemotherapy to receive IL3 10 mg/kg/day s.c. until hematologic recovery. Therapeutic success was obtained in 69.6% of cycles; a major response in 39.3% and a minor response in 30.3% of cycles. We obtained the best results in case of platelet count <49,000/mm3. The main toxicity was a flu-like syndrome. In two cycles (6%) we registered allergic episodes with flushing and lipothymia. In the 47% of cycles evaluable for toxicity no side effect was registered.