Approaches to the management of adolescents and young adults with acute leukaemia were investigated by sending a questionnaire to hospitals identified as having diagnosed or treated patients aged 15-29 years. The responses demonstrated the types of hospital treating these patients, the haematologists' perceived practice for entry of patients to Medical Research Council (MRC) leukaemia trials and reasons for non-entry. Data were linked to MRC trials data to determine the proportion of patients aged 15-29 years at diagnosis in responding hospitals actually treated in MRC leukaemia trials in the 5 years preceding the questionnaire. Eighty-two per cent of haematologists stated that they entered patients 'always' or 'whenever possible' for acute myeloid leukaemia (AML) and 76% for acute lymphoblastic leukaemia (ALL), but actual entry rates from the study hospitals were 46% of 239 AML patients and 36% of 182 ALL patients. The reasons most commonly reported for not entering eligible patients to national leukaemia trials were clinician preference for one arm of an MRC trial, a regional study or non-trial protocol, and concern about workload and ethical approval.