Colony-stimulating factors (CSFs) are hematopoietic growth hormones that stimulate the production, maturation, and function of white blood cells. The best studied are granulocyte-macrophage CSF (GM-CSF) and granulocyte CSF (G-CSF), both of which can be produced by recombinant DNA technology. Clinical indications for these agents include bone marrow failure secondary to administration of chemotherapeutic drugs or radiation, bone marrow transplantation, and a variety of congenital or iatrogenic neutropenias. Toxicity in usual clinical doses is mild, and consists mainly of bone pain and constitutional symptoms such as fever, headache, and myalgias. Interleukin-2 (IL-2) is a lymphokine that stimulates that multiplication of several types of killer cells. These cells can recognize and destroy foreign substances, such as tumors, without destroying normal cells. Major applications of IL-2 include treatment of patients with renal cell carcinoma, in whom the overall objective response rate is 15-30 percent, and malignant melanoma with response rates of about 18 percent. Combination therapy with other biologics and conventional cytotoxic drugs may increase IL-2's efficacy against these tumors. Toxicity is generally severe, but reversible. Hemodynamic toxicity, consisting of hypotension, edema, weight gain, and decreased renal function, is most characteristic. Suggestions are given for pharmacologic management of these and other IL-2 toxicities.