Oxatomide (CAS 60607-34-3), a diphenylmethyl-piperazine benzimidazole derivative is a new oral antiallergic drug useful in asthma in preventing allergic attacks. Using the model of citric acid-induced coughing in the unanesthetized, unrestrained guinea pig the antitussive effect of oxatomide was investigated. The animals were treated with logarithmically increasing doses of oxatomide (0.5, 1, 2 mg/kg, suspended in 0.5 ml of polyethylene glycol 200 + 0.5 ml of saline) and with the vehicle alone administered intraperitoneally (1 ml) 45 min before the challenge. Oxatomide reduced the number of coughs during the 3 min of challenge, lengthened the time of onset and reduced the number of coughs after cessation of the challenge significantly and a linear dose-effect regression was observed.