The cytostatic, molecular-targeted therapies becoming available forlung cancer and other human solid tumors are more likely to result instable disease than to produce tumor regression. In the setting ofadvanced lung cancer, stable disease provides significant benefit to thepatient. However, in the context of clinical trials, stable disease isvaguely defined, difficult to measure, and may represent a heterogeneouspatient population. The inclusion of alternative trial end pointssuch as symptom improvement and biologic activity may help to identifypatients who have achieved clinically relevant stable disease. Theepidermal growth factor receptor–tyrosine kinase inhibitor gefitinib(Iressa) has been shown to produce partial responses and stable diseasein patients with advanced lung cancer who have previously receivedtreatment with standard chemotherapies. In the monotherapy trials ofgefitinib, stable disease was correlated with improvements in diseaserelatedsymptoms and quality of life-the most meaningful end pointsfor the patient with advanced lung cancer. Thus, with the introductionof new molecular-targeted agents, stable disease with clinical benefitshould become an important goal of anticancer therapy.