Acute Newcastle disease virus infection following intranasal inoculation of chicks with a mesogenic strain of the virus produced a localized infection of the middle turbinate which was histologically demonstrable 18 hours after inoculation. There was destruction of mucous cells of individual acini in the under surface of the middle turbinate, and the infection rapidly spread to ciliated and goblet cells and to neighboring acini. By day 2 there was simultaneous remodeling of the mucosa, continued destruction and inflammatory infiltration and frequent loss of cartilage basophilia. By day 3 polymorphonuclear cells almost disappeared, epithelial mitoses commenced, and lymphocyte infiltration intensified; the plasma cells normally present along the lateral nasal gland ducts were often destroyed, very occasionally the glands themselves were destroyed. By days 5 and 6 inflammation greatly decreased, and by day 8 the mucociliated epithelium was essentially normal. The infection is sequentially comparable to acute mild rhinitis of man.