Adjustable drill string housings are described for use in the directional drilling of wellbores, e.g. wellbores for hydrocarbon recovery wells. The adjustable drill string housings permit adjustment of a bend angle in the housings without removing the housings from a wellbore. In some exemplary embodiments, the bend angle can be adjusted by changing the internal stresses in a support member carried by the housings. In other embodiments, the bend angle may be adjusted by causing failure of sacrificial support members carried by the housings, and the failure may be caused by delivering chemicals through a chemical delivery system to the sacrificial support members. Methods of operating the adjustable drill string housings include multi-lateral drilling operations wherein the bend angle is adjusted when a casing window has been detected.