Using the autoradiographic method in the zebra finch (poephila guttata), areas of the brain were identified which contain cells which accumulate testosterone. Among these areas are the caudal nucleus of the hyperstriatum ventrale, nucleus intercollicularis of the midbrain, and the tracheosyringeal portion of the hypoglossal nucleus of the medulla (nXIIts). These three are known to control or influence androgen dependent song and other vocalizations of passeriform birds, and nXIIts is composed of the motoneurons innervating the vocal (syringeal) muscles. Other areas containing hormone-concentrating cells are the medial preoptic area, nucleus periventricularis magnocellularis of the hypothalamus, dorsal infundibular layers, dorsomedial thalamus, lateral septum, magnocellular nucleus of the anterior neostriatum, periventricular medial neostriatum, nucleus taeniae of the archistriatum, and ventral paleostriatum augmentatum. Accumulation by cells in the preoptic area, hypothalamus, and limbic forebrain is consistent with a general vertebrate pattern of distribution of brain cells which accumulate sex steroids. Some of these same areas may be involved in the control of androgen dependent events such as courtship, copulation, aggression, and feedback regulation of the hypophysis.