Fourteen out of 21 non-Hodgkin lymphoma (NHL) and 3/11 chronic lymphoid leukemia cells (CLL) had the common acute lymphoid leukemia antigen (CALLA) All 32 patients had monoclonal B-cell proliferation. The CLL patients had 90% CALLA positive cells while the proportion of their leukemic elements was superior. Lymph-nodes or bone marrow invaded by a B monoclonal tumor cell population of NHL had significantly more CALLA positive cells (42.1 +/- 32.5%) than non-invaded tissues (11.4 +/- 10.3%). In NHL tissues with monoclonal B-cells, lymph-nodes had significantly more CALLA positive cells (56.0 +/- 29.9%) than marrow (23.5 +/- 27.7%). It is well known that the (CALLA) is not specific for ALL. It has been believed to be a differentiation antigen on pre B-cells. The present study confirms that it also occurs on B-cells (2,4,6,7,8,9,10,11).