Respiratory distress syndrome (RDS) in the newborn infants remains a major cause of mortality and morbidity in the newborn period despite much improvements in neonatal intensive care and artificial ventilatory techniques. Gastric fluid was obtained from 151 patients within 6 hours after delivery. The sensitivity, specificity, and predictive value of the simple shake test (133 cases) and stable microbubble rating (SMR) test (151 cases) were assessed in the diagnosis of RDS, as well as the relation between both tests and RDS. We carried out both tests of on gastric aspirates all newborn who admitted to NICU of Presbyterian Medical Center from June 1991 to August 1992. The results were summarized as follows: 1) Among the total 151 cases, RDS were found in 41 cases(27.2%). 2) RDS occurence rate of the simple shake test was 11/11 in 0 group, 17/26 in +1 group, 8/28 in +2 group, 2/41 in +3 group, and 2/27 in +4 group. RDS occurence rate was high the 0 and +1 group. 3) RDS occurence rate of the SMR test was 4/4 in very weak group, 32/36 in weak group, 1/33 in medium group, and 4/78 in strong group. RDS occurence rate was high in the very weak and weak group. 4) Among the positive group of the SMR test 95 cases, positive group of the shake test were found in 87 cases. Among negative group of the SMR test 38 cases, negative of the shake test were found in 29 cases (correlation coefficient=0.763). 5) Sensitivity of the shake test and SMR test were 70%, 87.8% respectively. Specificity of the shake test and SMR test were 93.3%, 96.4% respectively. Positive predictability were 75.7%, 90% respectively and negative predictability were 87.5%, 95.5% respectively. The shake test, as Well as SMR test, has significant value to diagnosis of the RDS. We predict RDS occurence rate of the SMR test was significantly higher than shake test.