A national survey of British radiotherapy schedules used in women with early breast cancer was undertaken to document variation in treatment practices and to consider its clinical significance. Although the variation is considerable, the analysis suggests that the majority of schedules in use are very similar in terms of treatment intensity when allowance is made for fraction size and overall time. Half the respondents used one of three dosage schedules, which probably differ very little in terms of late normal-tissue effects and tumour control from a conventional schedule giving 50 Gy in daily 2 Gy fractions. Eighty-two percent of respondents were using schedules that are equivalent to a dose of between 45 Gy and 50 Gy in 2 Gy fractions. The study suggests that the protocols in use by a minority of respondents may be unduly conservative or aggressive, and it leads to the proposal that oncologists should set up trials comparing commonly used schedules as a matter of urgency.