Single crystals of biotite have been shortened up to 20% in compression tests parallel to ,  and  directions at 3 Kbar confining pressure and temperatures from 300 to 700° C, and at a strain rate of 10-4 sec-1. Thick metal constraining sleeves were used and led to a distribution of kinking throughout the crystals. The orientation of kink boundaries, angle of bending and asymmetry of the basal plane across the kink boundaries and the axes of bending were measured. A minor amount of unidentified non-basal slip must have occurred to account for the assymmetry, but basal slip predominates at all temperatures. From the axes of bending, the discrete slip directions ,  and  for basal slip are deduced. Increase in temperature mainly leads to a simpler pattern of kinking associated with the kinks being wider and the kinking angle larger, presumably as a result of greater mobility of dislocation walls that form the kink boundaries.