The magnetization of a polycrystalline composite YBa2Cu3O7-x:Ag0.1 in the superconducting state is measured in the presence of a small a.c. magnetic field. With increase in field amplitude, the magnetization M(t) changes its shape from nearly sinusoidal to square-wave like and then to a two-peak structure. A similar behavior of the magnetization M(t), calculated from the critical-state model with intergranular critical current Jc=αc[μ(H0+|H|)]-1 is obtained. A very good fit is found between the theoretical and experimental results, and the parameters of the model are estimated. © 1992 Plenum Publishing Corporation.