We report a single-centre prospective audit of 29 lung cancer patients who were awaiting radical (potentially curative) radiotherapy. This was the total number assessed as suitable for radical treatment by one consultant during 1999. At the time of assessment they had been newly diagnosed and staged with a computed tomographic (CT) scan of chest. They had a subsequent CT scan prior to starting treatment for the purpose of planning the radiation fields. We have now measured tumour size on the diagnostic scans and compared this with the size on the planning scans. We have documented the delay between diagnostic and planning CT scanning and the total time between first hospital visit and starting treatment. Two patients had progression of symptoms while on the waiting list, making them unfit for radical treatment, and another four had tumour progression on planning CT such that the tumour volume was too large for radical treatment. Therefore, 21% of potentially curable patients became incurable on the waiting list. The delay between diagnostic and planning CT scans ranged from 18 to 131 days (median 54), with increases in the cross-sectional tumour size over that period ranging zero to 373%. The delay between the first hospital visit and starting treatment was 35-187 days (median 94); between the date of the radiotherapy request and the starting date for treatment it was 23-61 days (median 44). Limited access to specialists is the reason most often advanced for the poor performance of the UK in treating lung cancer. This study demonstrates that, even for the select minority of patients who have specialist referral and are deemed suitable for potentially curative treatment, the outcome is prejudiced by waiting times that allow tumour progression.