The blood concentration and urinary excretion of OE-7 (erythromycin stearate capsules) and control drug were investigated in 6 volunteers having gastroptosis. OE-7, newly arranged capsules containing erythromycin stearate, was investigated and obtained the results of high blood concentration by oral administration. To confirm the above, we measured blood concentration and urinary excretion of OE-7 comparing with ordinary erythromycin stearate capsules in 6 volunteers having gastroptosis. The peaks of blood concentration were noted at 3 hours after administration in 6 volunteers uniformly. The mean maximum blood concentration of OE-7 was 1.17 mcg/ml which was significantly higher than ordinary erythromycin stearate capsules. In time course of mean blood concentration, the blood concentration levels of OE-7 were higher than those of control erythromycin stearate capsules at any measurement. Effective blood levels were continuously high in OE-7. Urinary excretion of OE-7 reached to the maximum from 4 to 6 hours after administration which was also higher than control erythromycin stearate. Clinical efficacy of OE-7 was investigated in 28 cases in acute respiratory infection. The results noted were excellent in 5 cases (17.9%), good in 16 cases (57.1%), no change in 6 cases (21.4%), and undetermined in 1 case (3.6%). There were 5 cases of slight gastro-intestinal discomfort as the side effects. As the conclusion, OE-7 revealed good bioavailability and seemed to be useful antibiotic for acute respiratory infections.