The Oncology Nurses Study Group (ONSG) of the European Organization for Research and Treatment of Cancer (EORTC) initiated a survey to document the involvement of nurses in clinical trials. An English-language questionnaire was sent to 312 nurses in > 15 European countries. Results indicate that nurses lack training in oncology and in research methods. Nurses' tasks and activities are mainly oriented toward patient care. Nurses are rarely involved in activities related to protocol preparation and review. The circulation of information about clinical studies varies according to the center and the investigator responsible. Proposals to optimize nurse participation in clinical trials that were rated highly included (a) the availability of nursing protocol summaries translated into the local language, (b) contact with colleagues involved in the same trials, and (c) additional training in aspects of clinical trials related to nursing.