Quality of life (QL) is an important outcome in clinical trials in oncology. There is currently no valid international QL measure for gastric cancer. This paper describes the development of a QL module for gastric cancer to supplement the European Organization for Research and Treatment of Cancer (EORTC) Quality of life (QLQ-C30) questionnaire. Phases I to III of module development were conducted in the United Kingdom, France, Germany and Spain according to EORTC QL Group guidelines. Twenty relevant QL issues were generated from the literature and interviews with health professionals (n=24) and patients (n=58). This produced a 24 item provisional module. Further testing in 115 patients resulted in the QLQ-STO22, containing 22 questions, conceptualised into five scales and four single items, related to disease symptoms, treatment side-effects and emotional issues specific to gastric cancer. The use of the QLQ-C30 supplemented by the QLQ-STO22 will provide a comprehensive QL measure for international trials in gastric cancer.