Forty-four guinea-pigs were sensitized by intramuscular inoculation with the same amount (0.8ml) of 5% egg albumin in water. 3 weeks after sensitization, the animals were rondomly divided into 1 groups (group J as control; group II given small dose of piperitone 0.08ml/ 100g body weight; group J given large dose of piperitone 0.12ml/100g body weight; group IX given promethazine 2.5mg 100g body weight) and subjected to anaphylactic insult by intra-cardiac injection of 1ml of 5% egg albumin in water under the protection of different dosege of piperitone, a terpene from cymbopogon distans. given intramuscularly. Results of the experiment indicates that piperitone had significant dose-effect relation protective effect against the anaphylactic insult on the guinea-pigs and suggests that piperitone might be used clinically for the treatment of asthma