The detailing of wall-window interfaces and the consequences of defective installation of windows are an on-going concern in North America. This paper concerns laboratory evaluation of the water leakage performance of a select set of window-wall interface details. The details were for windows with mounting flanges installed in wood-frame walls sheathed with rigid extruded polystyrene foam. The tests were performed on a single full-scale test assembly in which two identical windows were installed by two similar but nonetheless different means. Each detail included a sill pan intended to collect water that gained entry into the assembly and thus was designed to be robust (tolerant of flaws). Tests were performed over a series of different water loading (spray) rates and over a series of different air pressure differentials at each spray rate. Air leakage rates through the window opening were monitored; they were controlled by a unique methodology. Leakage paths were introduced in the window frames, and these paths were alternatively blocked or opened to permit evaluation of the performance of the installation details under two different assumed conditions of window leakage. Air pressure distribution within the assemblies was monitored during spray testing. The wall assembly was designed to permit observation of water entry in it and to allow measurement of water entry to, or drainage from, various locations within the assembly. Results on water entry and management for the two wall-window interface configurations are given, and effectiveness of the details is discussed.