Forty-eight laminated specimens were made of 2 com. dental soft Si elastomers and in situ produced poly(Me methacrylate), aged at room temp. in artificial saliva for 1-360 days and studied for bonding strength in a destructive way by using a universal testing machine. The specimens were randomly divided into 8 groups differing in the soft lining materials and aging time. The adhesive interface was obsd. by scanning electron microscopy. The bonding strength depended only on the Si elastomer type. There was no statistical difference in bonding strength when the same Si elastomer was used. The bonding strength was higher than the required for clinical use (0.44 MPa).