To examine whether the variations in the expression level of Rho proteins in tumours might be related to histological grade, which is a generally used prognostic clinical parameter, we analysed the expression of RhoA-like GTPases (using an antibody cross-reacting with RhoA, B and C), Rac1, Cdc42, Rho-GDI and ERK2 in each of the six tumours classified as WHO grade I and grade III, respectively. The gene discussed is CDC42; the disease is neoplasm.