Abstract: The parameters of bioavailability for the single administration of aminophylline suppository or aminophylline tablet were investigated in 5 healthy volunteers. The converted values of the maximum blood concentration after administration of a suppository containing 360mg aminophylline or a tablet containing 200mg aminophylline are5.76±0.75ug/ml and 5.72±0.89 ug/ml, respectively. The average time of peak blood concentration for the suppository was found to be 6.71+0.41 hr and for the tablet 1.00±0.19hr. When tablets were used as control, the relative bioavailability of suppository was shown to be 0.82+0.08. These results show that absorption of theophylline from rectal suppositories of aminophylline was slower than that from tablets taken orally. Besides, some irritation on the mucous membrane of the rectum and/or some uncomfortable sensation (tenesmus) were experienced by volunteers who were given suppositories. Its other side-effects were slightly smaller than the tablets.