Studies have been carried out on the immobilization of spent ion-exchange resins produced in nuclear power plants in urea-formaldehyde matrix. The matrices were prepared by incorporating different types of ion-exchange resins in the pH range of 4.5 to 5.0, using boric acid as a catalyst. Characterization of the matrices was carried out with respect to dimensional changes, compressive strength, and leach resistance. The cumulative percentage weight loss and volume change were observed to decrease with the increase in boric acid concentration before attaining a plateau. The diffusion coefficients were in the order of 10(-16) M2/s, and the compressive strengths were in the range of 0.83 to 12 MPa. Infrared spectral studies on the urea-formaldehyde matrices revealed that the rate and the extent of cure depended on the type of resin.