The response ofthe vesicular glands and three specialized scent glands to testosterone administration after castration was studied in laboratory-reared Microtus montanus males taken from a recently established colony, which was begun with stock from northwestern Wyoming. The hip glands, obvious externally on the posterolateral region of the body. regressed markedly in experimental animals in the 6 to 8 weeks following castration. Following a 21-day series of injections oftestosterone propionate (seven doses), the correlation coefficients between dose and gland weight were 0.90 for vesicular glands, 0.46 for preputial glands, and 0.71 for anal glands. The correlation coefficients between dose and hjp gland measurements were 0.60 for length, 0.52 for width, and 0.59 for area. The results are discussed in the contexts of adaptive significance of the glands and the evolution of posterolateral skin glands among the microtine rodents.). Mamm., 59(4): 1978 772 by guest on June 9, 2016