An aerosol inhalation formulation containing a yeast-derived glycosylated recombinant form of human granulocyte macrophage colony stimulating factor (GM-CSF) with potential immunostimulating activity. Sargramostim binds to specific cell surface receptors, modulating the proliferation and differentiation of a variety of hematopoietic progenitor cells with some specificity towards stimulation of leukocyte production. This agent also activates neutrophils, monocytes, macrophages, and dendritic cells and promotes antigen presentation, upregulates antibody-dependent cellular cytotoxicity (ADCC), and increases interleukin-2-mediated, lymphokine-activated killer cell function. Aerosol inhalation may help achieve high concentrations of sargramostim in the lung.