Rainfall-runoff models are amongst the most important tools for the practical solution of flood estimation problems, as well as for theoretical investigations of controls on the flood frequency curve or for analysis of catchment and climate change. This article aims to provide a discussion of the use of rainfall-runoff modeling for flood estimation, with an emphasis on overall methodology rather than on specific hydrological models. After a brief introduction to some basic concepts of flood analysis, the article describes the two main approaches for applying rainfall-runoff models in flood estimation, namely, event-based modeling and continuous simulation. The theoretical basis for each approach is described along with typical model structures. Topics covered include rainfall models, hydrological model calibration and the estimation of parameters for modeling at ungauged or data-poor sites. The article concentrates on the development of the continuous simulation method, and includes a number of illustrations of its application, both from research studies and applied hydrology.