Immunotyping is an essential adjunct to cytomorphology for the diagnosis of lymphoma by fine-needle aspiration (FNA). Two independent techniques, cytospin preparations and flow cytometry, were used for immunotyping studies on 71 patients with histologically confirmed non-Hodgkin's lymphoma (63 B-cell lymphomas and 8 T-cell lymphomas). Diagnostic concordance between the two methods was obtained in 69 patients (97%). kappa, lambda, and CD3 (Leu-4) markers were routinely measured on all cytospins, and additional markers were requested when indicated. The standard panel measured by flow cytometry included 14 markers. In general, mean values of light-chain (kappa and lambda) immunoglobulins were consistently slightly higher by cytospin analysis than by flow cytometry. Light-chain immunoglobulin ratios (kappa/lambda or lambda/kappa) obtained by both methods proved to be reliable independent predictors of polyclonality or monoclonality. Correlation studies using the Spearman rank coefficient revealed good concordance among values of kappa, alpha, CD3, and CD5 obtained by the two techniques, suggesting that subjective quantitation by cytospins yields similar results to objective quantitation by flow cytometry. Cytospin analysis and flow cytometry appear equally capable of immunotyping aspirated lymphoid samples reliably. The advantages of each method are discussed.