Anaphylaxis or other serious allergic reactions reported. Use with caution in pre-existing cardiac problems (transient supraventricular arrhythmias reported in history of arrhythmias). Edema, capillary leak syndrome, pleural and/or pericardial effusion reported. Use with caution in hepatic impairment (bilirubin and transaminase elevations observed). Use with caution in renal impairment (serum creatinine elevations observed). Dyspnea may occur (use with caution in hypoxia, pulmonary infiltrates, or pre-existing lung disease). Simultaneous administration, or administration 24 hours preceding/following cytotoxic chemotherapy or radiotherapy not recommended. Solution contains benzyl alcohol, associated with «gasping syndrome» in neonates. If there is rapid increase in blood counts (ANC >20000/mm^3^, WBC >50000/mm^3^, or platelets >500000/mm^3^), decrease dose by 50% or discontinue drug. There is a «first-dose effect», seen (rarely) with first dose of a cycle and does not usually occur with subsequent doses within that cycle. May potentially act as growth factor for any tumor type, particularly myeloid malignancies (caution if used in any malignancy with myeloid characteristics; tumors of nonhematopoietic origin may have surface receptors for sargramostim). May interfere with bone imaging studies (increased hematopoietic activity of bone marrow may appear as transient positive bone imaging changes).