Kinetic studies were carried out on 6 benign and 37 malignant lymph nodes from patients with non-Hodgkin's malignant lymphomas (ML). The labeling index, DNA content, and cell distribution through the cell cycle were analyzed in the ML, which were classified according to the Kiel classification. Approximately 90% of the ML studied showed a clear diploidy; the only cases of polyploidy were limited to some centroblastic-centrocytic ML with more than 30% malignant centroblasts and to be single centroblastic ML. The labeling indexes ranged from 0.05 to 33%. No correlation was found between the proliferative rate and the degree of ploidy, while a grading of labeling index was found in relation to the three main DNA distribution patterns observed (i.e., G1 peak, S accumulation, and bimodal distribution through the cell cycle). From a kinetic point of view, the most heterogeneous groups were the lymphoplasmacytoid (subtype polymorphous) and centroblastic-centrocytic ML, where the degree of proliferation increased as the mixture of cell type (relative to the former group) and the malignant centroblastic component (relative to the latter group) increased.