Vinorelbine tartrate (Navelbine, Burroughs Wellcome Company, Research Park, NC) is a semisynthetic analog of vinblastine that has been approved by the Food and Drug Administration for use in the treatment of advanced, unresectable non-small cell lung cancer. It has a favorable safety profile and can safely and easily be administered in the outpatient setting on a weekly basis. The major toxicity is severe, granulocytopenia (absolute neutrophil count < 500 cells/mm3), that occurs in approximately 40% of treated patients. This granulocytopenia is rapidly reversible, and does not increase in severity with subsequent cycles. Despite the high incidence of granulocytopenia, only about 8% of patients require hospitalization for the treatment of febrile neutropenia. This article also reviews information concerning the incidence and management of the other major side effects including constipation, paresthesias, decreased deep tendon reflexes, myalgia, and injection site reactions. Guidelines for the safe administration of this agent along with suggestions for patient education are also presented. The potential significance of the impact that this new agent may have in the treatment of advanced, unresectable non-small cell lung cancer and advanced breast cancer is stressed.