Magnetic fields induce order and hence optical birefringence in suspensions of anisotropic, anisodiametric, and diamagnetic particles. Many colloids and latexes are sufficiently diamagnetic to exhibit this effect for relatively weak magnetic fields. An experimental and analytical procedure is used to interpret the responses of polydisperse polytetrafluorethylene latex suspensions to single-shot, low intensity magnetic pulses to give average size and size distribution data. The experimental results were compared with data from electron microscopy and showed good agreement. A rapid method of obtaining size distribution data from single measurements is thereby indicated.