It is essential to establish an objective and quantitative method for evaluating facial palsy and to measure the extent of paralysis in order to evaluate therapeutic efficacy, determine prognosis, select appropriate treatment and observe the process of recovery. This study utilized Moiré topography, which displays three-dimensional facial symmetry with high precision and is based on light interference theory, to determine the extent of facial palsy in 38 patients (20 men and 18 women) 5 months to 73 years of age. A stereoscopic lattice type Moiré camera (FM3013) was connected to a CCD camera and to the monitoring device for confirming Moiré stripes. Moiré photographs were taken with a thermal imager (FTI-200). The photos were visually and objectively evaluated on the basis of the Moiré pattern and were then input into a personal computer with a digitizer for data processing and analysis. To view the functions of facial nerve branches, five Moiré photographs were taken: at rest, wrinkling the forehead, closing the eyes lightly, blowing out the cheeks and grinning. Results indicated that the number of stripes and their polarization adequately reflected the function of individual facial nerve branches. Thus, a well-defined Moiré pattern could clarify the characteristics of the site and the degree of facial palsy and of recovery from paralysis. It is an analytical method that can be quickly applied and seems especially useful in infants and young children, in whom point-based assessment is difficult. It is possible to quantitatively evaluate facial palsy in terms of the Asymmetry Index (AI), which is 20-25% for severe paralysis, 12-19% for partial paralysis, and 5-10% for an essentially normal condition. However, the numerical value of the AI overlap in all three paralysis categories, indicating that quantitative assessment of paralysis would be difficult. Moiré topography is an excellent method of determining the extent of facial palsy, compensating for the short falls of examination-based assessment and permitting reproducible visual, objective, and quantitative evaluation.