Over a 9-year period ending in May 1990, 27 patients with histologically proved thyroid lymphoma were assessed and treated. There were 24 female and three male patients with a median age of 67 years at the time of diagnosis (age range, 39 to 85 years). The usual presentation was that of a rapidly enlarging neck mass. Incisional biopsy was the diagnostic procedure of choice; however, nine of 27 patients underwent diagnostic partial or total thyroidectomy based on a preoperative impression of thyroid carcinoma. All 27 patients had non-Hodgkin's lymphomas of intermediate (77%) or high (23%) grade. Detailed staging was carried out in 25 patients; seven patients (28%) had disease confined to the thyroid gland (stage I), while 18 (73%) had accompanying disease in cervical lymph nodes or the mediastinum (stage II). Combined multiagent chemotherapy and irradiation was given to 19 of 25 staged patients (76%). Actuarial, overall 5-year survival for all patients was 70% with 48 months being the median follow-up for living patients (follow-up range, 3 to 102 months). Of a number of factors evaluated using log-rank survival tests, only the absence of dysphagia at the time of hospital admission, a primary tumor mass not greater than 10 cm, restriction of disease to the thyroid gland, and the absence of mediastinal lymph node involvement were statistically significant predictors of improved survival. Surgery should usually be restricted to diagnostic biopsy, as there is infrequently a role for resection in the management of thyroid lymphoma, given the effectiveness of combined multiagent chemotherapy and radiotherapy.