Cytomorphology in conjunction with immunophenotypic characterization is becoming increasingly used for the primary diagnosis of non-Hodgkin's lymphomas (NHL). This combination is especially advantageous for the diagnosis of intra-abdominal and intrathoracic lymphomas, since unlike superficial lesions, open biopsy of deep-seated tissues is more invasive and more costly, and is associated with a higher risk. We report the cytologic and immunophenotypic features of intra-abdominal NHL obtained by fine-needle aspiration (FNA). Twenty-two cases of intra-abdominal lesions obtained by image-guided FNA where flow cytometry was also performed were reviewed. Of the 22 studied cases, 7 were classified as large-cell lymphoma, 5 as follicular center-cell lymphoma, 2 as small noncleaved-cell lymphoma, 2 as lymphoplasmacytoid lymphoma, one as small lymphocytic lymphoma, and one as marginal-zone lymphoma. In the remaining 4 cases where the immunophenotypic pattern was not definitive, the cytomorphologic features were of small cleaved cells in 3 cases and of mixed small cleaved and large cells in one case. We successfully classified 9 of the 10 patients on whom histologic confirmation was obtained. The successful primary classification of most intra-abdominal non-Hodgkin's lymphomas can be done with a combination of cytology and flow cytometry, and this can be the initial approach in patients with deep-seated lesions. Diagn. Cytopathol. 1999;21:98-104.