The results of a study undertaken prospectively in 1983 and 1984 to assess the value of computed tomography (CT) and conventional tomography in the planning of radiotherapy for laryngeal cancer are presented. Of 32 cases treated in 1983, 23 had both CT scans and coronal plane tomography prior to radiotherapy. At the end of 1983 these radiographs were reviewed and an assessment made of their value in treatment planning. As a result of this review it was decided that cancers of the larynx confined to the vocal cords should routinely have conventional coronal plane tomograms rather than CT scans. All other cases were to have CT scans and not tomograms. The results of following this policy in 1984 confirm that it is effective. There was no detriment to patients with early vocal cord cancers in performing coronal plane tomograms rather than CT scans. The survival at 24 months of both cohorts was 93%. In the more invasive cancers of the larynx, greater information about the extent of the disease was obtained using CT scans, and improved treatment plans resulted. When compared with a historical group, there appears to be an advantage for local control, 27.3% of the study group suffering local recurrence as opposed to 53.6% of the historical group.