Between 1968 and 1991, 237 patients underwent thyroidectomy for substernal goiter. Sixteen of them presented malignancies (6.8%). Mean age of the 159 women and 78 men was 57.7 years. Twenty-five patients had undergone previous thyroid surgery. The initial symptoms were cervical mass (72%), compression (16.2%), hyperthyroidism (13.1%), hypothyroidism (1.3%), and 5.5 per cent were asymptomatic. Most patients had long-standing goiter (mean duration: 12.9 yrs). All but eight operations were performed through a cervical incision. There were two postoperative deaths (0.8%), both in patients with advanced neoplasms. Early postoperative complications were hemorrhage (0.8%), dysphonia (4.6%), and transient hypocalcemia (2.9%). Five patients (2.1%) required tracheotomy. Complications were more frequent after total thyroidectomy than partial resection (P < 0.05), after surgery for malignancy than for benign disease (P < 0.05), and in complex than in simple forms (P < 0.05). One hundred ninety-four patients were followed after surgery; dyspnea was found in two patients (1.0%), dysphonia in seven (3.6%), and hypoparathyroidism in one. Analysis of our data indicates that 1) substernal goiter arose in elderly patients more than a decade later than cervical goiter; 2) goiters with a "complex" endothoracic development had an increased rate of short and long term complications; 3) cancer occurred in a significant number of patients, without any specific symptoms of malignancy; 4) the group of patients with hyperthyroidism was characterized by a significantly longer clinical history than euthyroid patients; 5) nearly all substernal goiters could be approached through a cervical collar incision; 6) the morbidity and mortality were low also after sternotomy.(ABSTRACT TRUNCATED AT 250 WORDS)