The effects of 4-weeks treatment with granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with peripheral artery disease were investigated in a phase 2 double-blind, placebo-controlled study. At 3 months, no differences were observed in peak treadmill walking time between patients treated with GM-CSF (n = 80) and those treated with placebo (n = 79). Patients treated with GM-CSF treatment did, however, have improved distance scores in the walking impairment questionnaire and physical function subcores in the SF-36 questionnaire.