A retrospective analysis of 215 differentiated thyroid cancers was undertaken to identify the various prognostic variables. There were 132 papillary and 83 follicular cancers; both histologic types occurred at an earlier age with a male to female ratio of 1:1. 1. There was a significant difference in the size of the primary tumours; 60/132 of papillary and 30/83 of follicular cancers were early TO-2 lesions and 20 papillary and 24 follicular cancers were advanced T3 lesions. Age did not affect the size of the primary tumour. Regional lymph node and pulmonary metastasis was common in both types of cancer while distant metastases occurred more frequently in follicular cancers (P<0.005). Following surgery, contralateral lobe recurrence in the remaining lobe was more common in follicular cancers while loco-regional recurrence after near-total thyroidectomy was more frequent in the papillary cancer group (P>0.05). Mortality in 26/132 papillary and 28/83 follicular cancer patients was high in both groups but significantly higher in follicular cancers (P<0.05). Although amongst papillary cancers mortality was higher in patients above 40 years of age (P<0.05), age did not affect survival in patients with follicular cancers. Sex did not affect survival in either group. The extent of the disease at presentation was found to be the most important determinant of survival with mortality significantly higher in T3N3M1 lesions (P<0.001).