Nasal sound are normally produced with an opened velopharyngeal part during pronouncing nasal consonants. Various disorders in nasal cavity and paranasal sinus can affect the resonance of nasal sounds, and results in change of nasality perceptually. Many instruments including rhinomanometry and accoustic rhinometry can assess the nasal possage dynamically and statically, but cannot assess the extent of nasality objectively. Recently, analytic methods with computerized equipments such as Nasometer and sound spectrogram are gaining wide attention to evaluate the nasality objectively. In this study, we assessed nasality using Nasometer and sound spectrogram in paitents with multiple nasal polyposis before and after endoscopic sinus surgery. With Nasometer, we measured nasalance which reflect the ratio of acoustic energy output from the nasal and oral cavities of the speaker. Nasogram slope scores were also measured for bilabial, alveolar, and velar nasal consonants. In the patients with multiple nasal polypsis, nasalance for mamma passage and nasogram slope scores for all nasal consonants were significantly lower than normal persons before surgery. After operation, nasalance and nasogram slope scores were significantly increased more than preoperative value. It seems to reflect the widened nasal passway after operation. On the sound spectrographic analysis, slight decrement of fundamental frequency of first nasal formant with increased amplitude was noted in all nasal consonants after operation. However, no significant change was noticed in fundamental frequency of second nasal formant. In conclusion, Nasometric and sound spectrographic analysis are considered to be useful tools for objectively assessing the extent of nasality(rhinophonia) brfore and after operation in the paitents with nasal airway obstruction.