The Dijon clinical and endoscopic staging system for intracavitary radiotherapy of rectal cancer takes into account the size and the depth of penetration of the rectal wall. Its prognostic value was evaluated in a series of 72 patients with rectal adenocarcinoma treated at the Centre de Lutte Contre le Cancer G. F. Leclerc in Dijon: 30 presented with a clinical stage (CS) T1A (purely exophytic tumors of less than 3 cm). The 5-year local relapse-free actuarial survival (LRFS) was 97%. Fourteen patients with CS T1B (infiltrative component and less than 3 cm diameter) had a LRFS of 77%. Nine patients with CS T2A tumors (with larger exophytic tumors) has a LRFS of 65%. Nineteen CS T2B cases (larger than 3 cm with an infiltrative component) presented a LRFS of 60%. The size of the tumor and the clinical estimate of the infiltration of the rectal wall both have a significant prognostic value: adenocarcinoma of less than 3 cm (n = 44) had a LRFS of 93% versus 59% in larger ones (n = 39; p = less than 0.01). Free mobile lesions (n = 39) did better (n = 33; LRFS = 86%) than infiltrated tumors (n = 33; LRFS = 66%; p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)