The present study is aimed at carrying out studies on SmBa2(Cu3-xMx)O7 and DyBa2(Cu3-xMx)O7 (M=Fe, Ni, Zn) in order to determine the solubility limit and the Tc suppression rate. Interestingly, the solubility limit is higher for M = Zn in both the Sm and Dy - 123 systems in contrast to the Y - 123 system. Resistivity (ρ{variant}-T) and susceptibility (χ-T) studies indicate that the initial rate of Tc suppression (upto ∼3 atom% of the dopant concentration) in both the systems lies in between that of Nd-123 and Y-123 systems. © 1994.