A method is presented for detg. the size distribution of spheres dispersed in a continuous phase by anal. of pulsed ultrasound signals reflected from members of the dispersion. Its theor. basis is developed for spherical bubbles and extended to nonspherical bubbles. It measures the relative diams. of differently sized spherical and near-spherical air bubbles rising singly through aq. polyethylene glycol. The ratios of measured diams. of smaller spherical bubbles to larger nonspherical bubbles rising singly or in swarms varied from those expected from photog. observations, because the larger bubbles deviated from the sym. ellipsoidal shape assumed in the calcn. method. Despite this difficulty, which can be overcome by standardization, use of pulsed ultrasound reflection may offer the 1st soln. to bubble-size distribution measurements in opaque, multiphase, and viscous fluids. The expts. were carried out in a tank and an air-lift column. [on SciFinder (R)]