Hosting user interface controls in a window via an interface for controlling the window is disclosed. One aspect of the invention is a computerized system having an operating system and at least one program. The operating system provides for hosting controls of a predetermined type within windows of a predetermined type via an interface for controlling the windows. The programs utilize the interface to host one or more controls within one or more windows. Thus, with respect to versions of the MICROSOFT WINDOWS operating system, a program may utilize the WIN32 API (i.e., interface) to host ACTIVEX-type controls within windows hosted by the program, also via the WIN32 API.