Immunoglobulin quantitation was performed on pretherapy sera from 120 patients who had non-Hodgkin's lymphoma in an attempt to correlate abnormalities with histologic cell type and pattern. Patients with diffuse lymphomas had significantly (P less than 0.05) higher levels of IgG and IgA than patients with follicular lymphomas. Furthermore, polyclonal hyperimmunoglobulinemia was overall more common than hypoimmunoglobulinemia, and abnormally high immunoglobulin levels were most frequently found in patients who had diffuse histologic patterns. The highest values were associated with either lymphomas composed of T (thymus-derived) cells or large B (bursa-derived) cells. The incidence of quantitative immunoglobulin abnormalities in patients with T-cell lymphomas was comparable with that in patients with B-cell lymphomas. These abnormalities in the former group of patients were exclusively above the normal range, whereas they were equally above and below the normal range in the latter group. The frequent polyclonal hyperimmunoglobulinemia in patients with T-cell lymphomas may be related to the pathophysiology of these lesions.