Data will be presented on some effects of noise exposure on early physical and behavioral development in the albino rat (Rattus norvegicus). Twenty-four rat pups, age 9 days, were divided into three groups of eight pups each, matched by weight. One group was exposed to continuous narrow-band noise at a level of 80 dBA for 3 h on each of 30 successive days. A second group was exposed to the same noise for 3 h on each of 30 days at a level of 100 dBA. The third group (control group) was observed for 3-h periods for 30 days in the colony room with an average ambient noise level of about 60 dBA. The weight of each animal was measured daily. Behavioral measures (grooming, sleeping, play, locomotion-active, and locomotion-stationary) were taken during the 1st and last 15 rain of each of the sessions. Open field measures were taken on the last 3 days. The animals were then sacrificed, and their stomachs and adrenal glands were removed for histological examination. In terms of the behavioral measures taken, the 80- and 100-dB group showed greater activity levels, with incidence of grooming being the most affected. The animals exposed to 100-dB noise showed least weight gains. Stomach ulceration occurred only in the 80- and 100-dB groups. Adrenal gland weights of the 100.rib animals tend to be larger than those of the other groups.

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