Six one-week-old piglets were pretreated with a 1% acetic acid solution for two days in one or both nostrils. Three piglets were not treated with acetic acid. Three days after treatment all nine piglets were inoculated in both nostrils with a toxigenic type D strain of Pasteurella multocida. Three piglets were killed seven days after inoculation; one died spontaneously 13 days after inoculation and the remaining pigs were killed at approximately 90 kg body weight, i.e., five to six months of age. All acetic acid-treated animals developed severe atrophy of the turbinates in the treated nostrils. Untreated nostrils were normal. The present results showed that toxigenic P. multocida can induce turbinate atrophy that persisted until 90 kg body weight when the lesions were similar to spontaneous atrophic rhinitis in pigs. The turbinate atrophy was not accompanied by inflammatory reaction, atrophy of other bone structures, or lesions in other organs. The experiment showed furthermore that toxigenic P. multocida may be present in the tonsils of control animals without causing turbinate atrophy. A pathogenesis for atrophic rhinitis in pigs is proposed.