The paper presents a case history related to the interaction of a compressor, its concrete block foundation and the supporting soil system. The owner of the compressor asked the Romanian National Center for Earthquake Engineering and Vibrations to solve the problem of the excessive vibration amplitudes that put the compressor out of service at a short time after starting to operate. The first step that was made was the in situ performance of measurements, in order to establish the dynamic properties of the compressor foundation, as well as the amplitudes of the vibrations at the operating speed. The design of the foundation was then checked, in order to determine if it has been designed taking into account the demands of the manufacturer. It should be stressed here that the poor performance of the compressor was due to a faulty design of the foundation, to a faulty construction, and to inadequate geotechnical information, that led to unrealistic soil data used in estimating the foundation response. The purpose of the evaluation was to establish whether remedial measures were to be taken to reduce the foundation’s vibration amplitudes to permissible levels, or to redesign the foundation completely
