In non-Hodgkin's lymphoma (NHL), the precise analysis of non-neoplastic immunocompetent cells in lymph nodes may be important to understand the pathophysiology of anti-tumor immunity. We have investigated such immunocompetent cells of 14 patients with B-cell type NHL (B-NHL) by flow cytometry, and compared them with the data obtained from 10 patients with reactive lymphadenopathy. The results on B-NHLs were as follows; CD3+ (T lymphocyte) = 45.0 +/- 19.7%, CD4+/CD3+ = 62.7 +/- 14.2%, CD4+CD45RA-/CD4+ = 82.9 +/- 8.1% (Control 62.9 +/- 14.5%, p < 0.01), CD4+CD29++/CD4+ = 29.2 +/- 7.0% (Control 42.6 +/- 12.9%, p < 0.01), CD8+/CD3+ = 36.0 +/- 11.3%, CD8++S6F1++/CD3+ = 23.2 +/- 10.6% (Control 9.1 +/- 4.3%, p < 0.01), CD8++S6F1++/CD8++ = 75.3 +/- 16.7% (Control 41.5 +/- 19.6%, p < 0.01), CD3-CD56+ cells = 1.0 +/- 0.7% (Control 2.2 +/- 1.6%, p < 0.05). These findings suggest that CD4+ T lymphocytes in lymph nodes of B-NHL may change to memory cells (CD45RA- cells), but such memory cells could only weakly express CD29 molecules which are thought to play an important role in the manifestation of helper function. This phenotypic discordance of CD4+ T lymphocytes may produce incomplete anti-tumor immunity in B-NHL.