Any extensive analysis of Hodgkin (H) and Reed-Sternberg (RS) cells is limited by the scarcity of available material and by the common contamination with "by-stander" cells. The establishment of Hodgkin's disease-derived cell lines provides the opportunity to undertake studies in which large numbers of cells are required, as these cell lines are by definition monoclonal populations with unlimited cell growth. In this study, we analyzed the enzyme profiles of eight Hodgkin's disease cell lines (Co, Ho, Fox, HDLM-2, KM-H2, L428, L540, and L591) whereby cellular alpha-naphthyl acetate esterases, acid phosphatases, and dipeptidylpeptidase IV were examined quantitatively or qualitatively by IEF or chromatographic techniques. The results indicate that all of the H-RS cell lines examined had enzymatic features typical for lymphoid cells and, in particular, a monocyte/histiocyte origin of the cell lines could be excluded. Extrapolation of the available immunological, molecular biological, and enzymological evidence gained in vitro on cultured representatives of H-RS cells suggests a lymphoid origin for in vivo H-RS cells.