The renin-like principle of the submaxillary gland of the white mouse has greater activity in males than in females throughout the lifespan of 3-36 weeks. Dependence of this difference on male sex hormone was shown by: reduction in renin-like activity in males after castration; restoration of activity in castrated males by therapy with testosterone; enhanced activity in females given testosterone treatment. Following ligation of the common submaxillary duct, renin-like activity decreased within 3 days, and was nearly undetectable after 7 days. These studies suggest that the renin-like substance present in the mouse submaxillary gland is 1 of the androgen-dependent proteolytic enzymes of the excretory ducts and is associated with exocrine function of the gland. Its specific function is not known.