Non Hodgkin lymphomas (NHL) of the thyroid are rather uncommon and account for about 7.7 p.100 of the tumours of the gland. They are remarkable by their usual occurrence in patients with Hashimoto's disease and by controversy about their therapy. The clinical features and the course of four additional cases occurring in four female patients (ages ranged from 61 to 73 years) are reported. The clinical picture was that of a quickly growing diffuse or multinodular goiter, squeezing surrounding neck structures. Antithyroid antibodies were present in 3 cases; microscopical examination showed cytologic features of lymphocytic thyroiditis. Two patients died within a few months, the follow-up is about two years for the others. Two main problems are discussed. First, NHL of the thyroid usually occurs in patients with Hashimoto's disease: how to confidently recognize lymphomas by fine needle biopsy in such cases? Second, which is the best treatment? The authors think that lymphomas of the thyroid have to be considered rather as lymphomas than thyroid tumours. Therefore the cure of the disease may need chemotherapy, in some cases associated with radiotherapy according to careful staging and grading in each case.