The development of microcrystalline cellulose has made available to the pharmaceutical industry an extremely valuable tableting agent. It was found that tablets of plain microcrystalline cellulose will tend to soften and swell when exposed to humid conditions, but the effect is reversed upon the removal of increased humidities. Elevated temperatures have no effect on these tablets. Microcrystalline cellulose tablets will disintegrate very slowly in solvents of a relatively low polarity. It is postulated that tablets of this material are a special form of cellulose fibril in which the individual crystallites are held together largely by hydrogen bonding. Tablet disintegration is merely the breaking of the intercrystallite bonds by the disintegrating medium. No significant separation of components was found during the compression of a microcrystalline cellulose-containing formulation. The release of amphetamine sulfate and sodium phenobarbital from tablets containing micro-crystalline cellulose is excellent. Determinations after 10 weeks at various environments indicate that no release problems exist. When the cellulosic compound was used as a dry binder—disintegrator in the direct compression of formulations of ephedrine hydrochloride, quinine sulfate, and a low melting steroid, tablets of outstanding quality were produced.