Ten anatomic territories, including both lateral pterygoid muscle and temporomandibular joint heads, were explored with magnetic resonance imaging in subjects with no dysfunctional disorders. The sequence used was one of inversion-recovery, supplemented with image contrast reversal for better visualization. The muscles were observed in the resting position and in dynamic relation. Slice plane definition provided information on the anatomic variations of the superior head and on the muscle-articular junction, in particular on the fascicular aspect of the superior lateral pterygoid muscle and on the differentiation between condyle insertions under effort. The choice of technique and the results are discussed. Avenues are opened for the exploration of muscles utilizing magnetic resonance imaging.