Image analysis with a SAMBA 2005 (ALCATEL-TITN, Co) was used to quantify the Ki-67 stained area percentage in 46 T-cell malignant lymphomas (T-ML), classified according to the updated Kiel classification. This parameter demonstrated correlation with the number of Ki-67-positive cellular profiles (r = 0.88, P less than 0.001) and was more reproducible than cell counting. A significant difference was found between low and high grade T-ML (mean values +/- SEM respectively of 10.20 +/- 1.82 per cent and 25.63 +/- 3.15 per cent). The most interesting findings were that: (1) AILD-type T-ML showed an intermediate proliferation rate (15.55 +/- 2.72 per cent) between pleomorphic T-ML with medium and with large cells (respectively 12.53 +/- 3.64 per cent and 22.43 +/- 3.46 per cent), both of which belong to the high grade malignancy group. This finding is in accordance with the poor prognosis of this subtype despite its classification in the low grade malignancy group. (2) Subclassification of the pleomorphic MLs according to the predominance of small, medium or large cells, demonstrated significant differences between these three subtypes. However, the great overlap of values between pleomorphic T-ML with medium and with large cells, seems to indicate that the subclassification of these two subtypes is less valid. (3) A wide range of values with overlap was observed in AILD-type ML, in pleomorphic with medium or large cells and in lymphoblastic T-ML: for these T-ML with variable survival courses, the Ki-67 area percentage, one parameter of proliferative activity, appears worth studying as a prognostic factor.