Inspection based maintenance strategies can provide an efficient alternative for ageing civil engineering components subjected to ageing and degradation. The technical and/or economic efficiency of such strategies depends on many factors such as the availability, cost and efficiency of inspection techniques, the mechanisms involved in the loss of performance, the relation between what can be measured through inspections and the level of performance of the structure, the level of required serviceability of the structure, and the direct and indirect economic losses due to a reduction in the performance of a structure. On this basis, this paper studies, using Monte Carlo simulations, the benefits and limitations of an inspection based maintenance strategy. The quality of the inspection technique is analyzed in terms of its sensitivity to defects in their initial stage of development, and on its discriminant ability (detection of a real defect, while avoiding false alarms). The study is carried out in a general context, but is fed with data and models used in the MEDACHS Project, devoted to the analysis of maintenance and reliability of ageing structures in a marine environment. More specifically, the efficiency of inspection based maintenance and systematic maintenance is compared, under different conditions.Read less <