the purpose of the present study was to test a wide range of doses of soman for the purpose of describing dose-related changes in respiratory function. adult cata anesthetized with alpha-chloralose were used and respiratory activity was monitored with a fleisch pneumotachograph. soman was administered by topical application (drug was added to cottonoid pledgets) to 3 sites on the surface of the ventrolateral medulla. these were the rostral, intermediate and caudal areas. the greatest effect of soman occurred at the intermediate area. doses of 0.004, 0.01, 0.04, 0.1, 0.25 and 0.5 ug/side increased tidal volume by 2 + or - 0.3, 4 + or - 1, 53 + or - 15, 38 + or - 10, 48 + or - 5 and 92 + or - 19 ml, respectively doses of 0.01, 0.04, 0.1, 0.25 and 0.5 mu sub g/side produced significant decreases in respiratory rate. with the 3 highest doses, the decrease in rate was preceded by an increase in respiratory rate these effects of soman were mediated through activation of cns muscarinic receptors since they were blocked by local application of atropine. determination of cholinesterase activity at the ventrolateral medulla revealed a high degree of activity at the intermediate area where soman exerted its most intense respiratory effect. (sdw)