A lack of information on the effectiveness of fire safety systems, including sprinklers, has been noted as being a limiting factor in the development of performance-based fire safety design. Of the fire safety systems available, sprinkler operation has been studied most extensively. This paper reviews the information currently available on sprinkler effectiveness in fires. Two approaches are generally taken for estimating sprinkler effectiveness: component-based approaches using a fault tree or similar method and system-based approaches using fire incident data where sprinklers were present. In this paper, sprinkler system component data and effectiveness estimates from system-based studies have been compiled and tabulated, with a comparison of the merits of the two approaches. Recommendations for using the data for design purposes are made, including considerations for uncertainty and using a hybrid system/component approach for specific sprinkler system comparisons. These recommendations provide input on the reliability of systems in the development of performance-based fire safety design methods.