Cover Sections through the perineum of male (left) and female (right) rat pups illustrate androgen-dependent sex differences in the size of the bulbocavernosus (BC) and levator ani (LA) muscles. Androgen receptors in muscle fiber alone do not appear to mediate this sex difference, or that in the innervating spinal nucleus of the bulbocavernosus motoneurons. From the article in this issue by Niel et al., pages 3207–3213.