Continuous monitoring and inspection of large dams would provide means for proper rehabilitative actions to be taken on time which intend to maintain the desired safety throughout the physical life of dams. Comprehensive inspections can be carried out using a number of instruments. An ideal dam instrumentation system should provide time-dependent information about critical parameters so that possible future behaviour of the structure can be predicted. Numerous of the existing dams do not have adequate instruments or current instrumentation systems may not be in good condition. By implementing the modern equipment to existing dams, the uncertainty associated with the impacts of aging or unexpected severe external events will be reduced and possible remedial measures can be taken accordingly. This paper addresses the concept of instrument retrofitting to an unmonitored structure, Gokcekaya Dam, 159 m-high arch dam, Turkey, with reference to investigation of the current condition of the structure. The deficiencies observed are listed and the corresponding rehabilitative measures are suggested. Finally, different alternatives of a new instrumentation system are introduced and compared in monetary terms.