The purpose of this protocol is to determine the phase II response rate of melanoma and renal cell cancer to therapy with Topotecan, a topoisomerase I inhibitor and to determine whether granulocyte-macrophage colony stimulating factor (GM-CSF) given before chemotherapy prevents myelosuppression. All patients receive Topotecan 1.5 mg/m2 daily by bolus intravenous infusion for five days and post-therapy GM-CSF 250 ug/m2 daily. Patients are randomized to receive no additional therapy or (3M- CSF 250 ug/m2 twice daily before Topotecan. Fifty-two patients have been entered on study, twenty-seven patients with melanoma and twenty-five with renal cell cancer. Forty-nine patients are evaluable for response, twenty-five with melanoma and twenty-four with renal cell cancer. One patient with melanoma remains active on study and has not been evaluated for response. One patient with renal cell cancer had complete regression of his lung metastases but no response in his kidney primary. One patient with melanoma had a partial response of his subcutaneous disease that lasted for six months prior to developing brain metastasis. No other responses have been seen. A decrease in grade IV neutropenia following both the first and second cycle of Topotecan has been seen in patients randomized to prechemotherapy GM-CSF. No protective or adverse effect on platelet counts was seen in patients treated with GM-CSF before chemotherapy.