A thermostatic valve assembly includes three housing components (16, 18, 20) containing two interconnected chambers (64, 78). A first thermally responsive valve unit (68) is disposed in the chamber (64) while a second thermally responsive valve element (98) is disposed in the chamber (78). Both the chambers (64) and (78) have inlets (60, 110) and the chamber (64) has an outlet (66). The valve may assume configurations allowing a minimal flow (FIG. 2), a large volume warm up flow (FIG. 3), a mixed flow regimen (FIG. 4) and a pure cooling flow regimen (FIG. 5).