Fine needle aspirates from 54 consecutive patients with primary or recurrent blastic (high-grade malignant) non-Hodgkin's lymphomas (NHLs) were analyzed by cytomorphology and immunocytochemistry. The cytologic diagnoses induced follicular center-cell-derived (centroblastic or anaplastic centrocytic) lymphoma (31 cases), immunoblastic lymphoma (11 cases), lymphoblastic lymphoma (9 cases) and histiocytic lymphoma (3 cases). Immunocytochemistry showed a B-cell phenotype of the neoplastic lymphocytes in all lymphoblastic lymphomas, 29 follicle center-cell lymphomas and 4 immunoblastic lymphomas. Four of the immunoblastic lymphomas were of T-cell origin while one case was not evaluable due to necrosis. A histiocytic origin was confirmed in two of the three cases that had a cytologic diagnosis of histiocytic lymphoma; the third case was shown by immunocytochemistry to be a true Ki-1-positive large cell lymphoma. Histologic and immunohistochemical analysis were performed on surgical biopsies from 18 patients. The results were in agreement with those on the fine needle aspiration (FNA) material in 14 cases. Three lymphomas could be phenotyped on aspirated material while marker studies on excised material were inconclusive. One lymph node aspirate contained mostly necrotic cells, which were unsatisfactory for adequate immunocytochemistry. However, sections from a removed tonsil from the same patient could be used for conclusive histology and phenotyping. In conclusion, the high diagnostic accuracy of combined cytomorphologic and immunocytochemical assessment of FNA samples validates the use of the technique in the diagnostic work-up of blastic (high-grade malignant) NHLs. In fact, the diagnostic accuracy seems so high that the technique can safely be used in the final diagnosis of blastic NHLs.