A multiple myeloma-specific quality-of-life questionnaire module has been designed in collaboration with the EORTC Quality-of-Life Study Group to be used in clinical trials with the EORTC QLQ-C30, a general cancer questionnaire. Strict methodology was employed to ensure thorough and appropriate development of the module. An extensive literature review was performed to identify health-related quality-of-life issues relevant to patients with multiple myeloma. Semi-structured interviews were then carried out in several European countries with health-care providers experienced in the treatment of patients with multiple myeloma, and with a group of patients with multiple myeloma, to identify the issues which were most important to patients. A questionnaire was devised from the list of issues, using a 1-week time-frame and response categories consistent with the EORTC QLQ-C30. The provisional questionnaire and the EORTC QLQ-C30 were administered to patients with multiple myeloma in each participating country with further semi-structured interviews to refine the content and design of the questionnaire. A review of the results obtained in each stage of development resulted in a 24-item myeloma-specific module, the EORTC QLQ-MY24, which assesses disease-specific symptoms and their impact on everyday life, treatment side-effects, social support, and future perspective. The module is currently undergoing further international field-testing to assess its psychometric properties.