The effects of reserpine and α-methyl-p-tyrosine on the occurrence of vaginal opening were studied in rats. Reserpine decreased hypothalamic norepinephrine content and delayed vaginal opening. However, it also caused a decrease in the rate of body weight gain, and a comparable decrease in body weight gain produced by restricting food intake also inhibited the onset of puberty without reducing hypothalamic norepinephrine content. α-Methyl-p-tyrosine decreased hypothalamic norepinephrine without affecting the onset of puberty. After puberty, the animals treated with both drugs showed periods of prolonged diestrus, indicating that the drugs were affecting the secretion of gonadotropic hormones. These results suggest that brain catecholamines are not involved in the control of vaginal opening in the rat.