The nutritive evaluation of range forages often is limited by the size of the forage sample available, by the difficulty of determining both the quantity and quality of the forage eaten, and by the labour and other costs of making total faecal collections in digestion trials under range conditions. Microdigestion techniques utilizing either the nylon bag in the rumen (hereafter referred to as nylon bag in vivo) and artificial rumen techniques (hereafter referred to as in vitro) have been reviewed by Annison & Lewis (1959), Barnett & Reid (1961), and Johnson (1963). Forage evaluation could be greatly simplified if such microdigestion techniques could be utilized under range conditions. Following preliminary studies (Van Dyne, 1962), the research reported in this paper was undertaken to evaluate these techniques under both range drylot conditions in studying the intake and digestion of forages. Other aspects of these trials are reported elsewhere (Van Dyne & Weir, 1964; Van Dyne & Meyer, 1964; Van Dyne & Lofgreen, 1964; Van Dyne & Heady, 1965a, b).