Combination therapy with gemcitabine hydrochloride and erlotinib hydrochloride was administered to 4 patients with unresectable advanced recurrent pancreatic cancer, and adverse reactions and compliance were investigated. Anorexia was noted as an adverse event in 3 patients. The protocol was continued by dose reduction of erlotinib in 2 patients. One patient survived up to 23 months. These findings suggest that maintenance of drug compliance can be achieved by adjusting the dose of erlotinib and that this influences the antitumor effect.