Rhelogoical properties of three recent mudflows at Mount St. Helens were estimated using technique developed for deterimining the properties of debris flows based on the geometry of their deposits. Calculated yield strengths of 1100, 1000, and 400 Pa, maximum flow velocities of 10 to 31 m/s, volumetric flow rates of 300 to 3400 m3/s, and plastic viscosities of 20 to 320 Ps-s all compare favorably with measured and estimated values cited in the literature. A method for determining likely sites of future mudflow initiation based on these data is outlined.