We researched aging of the LRB (Lead Rubber Bearing) installed in a base-isolated building which was constructed 15 years ago. The hardness of the cover rubber and the height were measured for 35 LRBs which were installed in the building. The compression test and combined compression shear test with monitor samples and actually installed LRB were performed to search changes in their hysteresis characteristics. The monitor samples were composed of 4 LRBs and 1 RB. Main results obtained were as follows: 1) The LRBs installed in the TC building crept approximately 1 (mm) during 15 years and did not changed during last 5 years. 2) The hardness of the cover rubber did not change against that of 15 years ago. 3) From the testing of the monitor samples, the compression stiffness increased approximately 17% and the shear stiffness increased approximately 5%, however the yield force changed quite a little during 15 years on average. As a result, the suitability of the design specifications of the LRB was confirmed.

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