High-dose chemotherapy followed by haematopoietic stem cell transplantation can be associated with high physical and emotional distress levels and reduced quality of life. Systematic prospective measurement of impact of therapy on patient quality of life can aid treatment choices and provide better patient information. We describe the development of a high-dose chemotherapy questionnaire module to supplement the European Organisation for Research and Treatment of Cancer Core Questionnaire (EORTC QLQ-C30). Phases 1-3 of module development were conducted in United Kingdom, Germany, Austria and Norway, according to EORTC QOL Group guidelines. Forty-eight quality of life (QOL) issues were generated from the literature searches and interviews with health care professionals (n=24) and patients (n=92). This produced a 50 item provisional module. Further testing in 169 patients resulted in the QLQ-HDC29 module, containing 29 items, conceptualised into six multi-item scales and eight single items. The EORTC QLQ-C30, supplemented by QLQ-HDC29 will provide a comprehensive QOL measure for the international clinical trials of high-dose chemotherapy.