Aerosol formulations of ondansetron useful for pulmonary delivery are provided. The formulations are useful in the reduction, elimination or prevention of nausea and vomiting associated with chemotherapy, radiation therapy, and surgery. Also provided are novel methods to treat chemotherapy-induced nausea and vomiting (CINV), radiation-induced nausea and vomiting (RINV), and post-operative nausea and vomiting (PONV) using the inhalation formulations.
