A high-resolution two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) was used for total cellular polypeptide mapping of two established lymphoma cell lines; MANCA, a Burkitt's line representing a high grade lymphoma (HGL) and WSU-NHL (nodular histiocytic lymphoma) representing an intermediate grade lymphoma (IGL). Gels were digitized and analysed with an image scanning computer using the Elsie 4 system. Polypeptide mapping revealed striking similarities in 1100 polypeptide spots in both types. However, three polypeptides were unique to HGL (Molecular mass/isoelectric point (Mr/PI): 39/4.4, 35/5.6, 33/4.8), and one to IGL (95/4.7). In order to investigate the kinetics of expression of these polypeptides, the two cell lines were treated with two protein kinase C (PKC) activators, tumour promoting 12-O tetradecanoylphorbol 13-acetate (TPA) and bryostatin 1. 2D-PAGE of the treated cells revealed that the HGL line loses its unique polypeptides and expresses a new one. The new polypeptide has the same Mr and PI as that unique to the untreated IGL (95/4.7). TPA or bryostatin 1 treatment of the IGL line for 72 h induced no significant changes. Our data show a unidirectional change from HGL to IGL, supporting the clinical notion that HGL is less differentiated than IGL. It also shows the similarity in the mode of action of bryostatin 1 and TPA in inducing these polypeptide changes.