The progress of salivary gland morphosis was followed by microscopic examination of serial histologic sections of the heads and necks of rats at age intervals from 13 days in utero to two days postnatally. The anlagen of the submandibular and sublingual glands appear late in the thirteenth or early in the fourteenth day in utero, with the submandibular anlage appearing first. The parotid anlage appears last, later in the fourteenth day in utero, and is located in the buccal wall near the angle of the mouth. The cells of the anlage proliferate to form a narrow cord (the future Stensen's duct) with a cluster of cells at its distal terminus. By 16 days in utero, the terminal cluster has migrated to the vicinity of the developing mandibular ramus, at which point it begins to ramify. Ductal lumena begin to form at 17 days in utero, but the ductal system is not patent until 20 days in utero. These findings indicate that secretions of the parotid gland cannot enter the oral cavity until about two days before birth. The ductal systems of the submandibular and sublingual glands are patent at 17 days in utero, and morphologically both glands appear to be at a more advanced developmental stage than the parotid at the time of birth.