Between 1968 and 1991, 190 patients (51 men, 139 women) with a mean age of 46.3 years underwent surgery for differentiated thyroid cancer (148 papillary and 42 follicular carcinomas). In 29.5% of the cases a concomitant goitre was histologically demonstrated. These patients were significantly older (mean: 54.7 years) (P<0.01). The patients who had previously received cervical radiotherapy were significantly younger (mean: 29.7 years) (P<0.01). The analysis of historical and clinical findings failed to identify predictive factors of biological aggressiveness. Hyperthyroidism occurred in 5.7% of patients: this subgroup did not show any difference in clinical behaviour. Occult carcinoma (14.7%) and multifocality (9.4%) were found more frequently in the glands with a pre-existent goitre (P<0.05), but the clinical significance of these aspects is uncertain. The surgical treatment of choice was total thyroidectomy (135 patients); more conservative procedures were performed only in younger patients with small lesions, without a difference in survival. Post-operatively a permanent recurrent laryngeal nerve injury occurred in four patients (2.1%) and nine patients (4.7%) required a permanent calcium supplementation. Among patients in follow-up (91.6%), those who underwent a total thyroidectomy were studied using a total body scinti scan. A poor prognosis was associated with age (>40 years), pT, stage, pM and symptomatic metastases.