Background: Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) are simple, convenient, and non-in-vasive method to measure respiratory muscle strength at the mouth, but standards are not clearly established. This study was performed to obtain the normal predictive values of the MIP and MEP of Korean adult. Methods: Among 561 patients who visited clinic of family medicine in Pusan National University Hospital for health check, 107 people (62 men, 45 women) were recruited after excluding past history or underlying disease from December, 2010 to April, 2012. We measured MIP and MEP in sitting position using handheld respiratory pressure meter (MicroRPM, Micro Medical Ltd). Results: Mean values of MIP and MEP were 61.40±21.66 kPA and 71.73±17.91 kPA. Mean values of MIP and MEP of men according to age are as follows: 22men (30-39 years old), MIP=71.68±14.55 kPA and MEP=92.41±15.96 kPA; 19 men (40-49 years old), MIP=75.74±15.29 kPA and MEP=89.89±15.41 kPA; 21 men (50-59 years old), MIP=68.14±22.74 kPA and MEP=81.14±20.52 kPA. Mean values of MIP and MEP of women according to age are as follows: 19women (30-39 years old), MIP=52.37±21.20 kPA and MEP=57.89±15.91 kPA; 11women (40-49 years old), MIP=45.09±15.44 kPA and MEP=59.64±8.65 kPA; 15 women (50-59 years old), MIP=42.13±18.11 kPA and MEP=58.38±14.12 kPA. Conclusion: We report normal values of respiratory muscle strengths according to sex and age after measuring the MIP and MEP in healthy Korean adults.