A QUANTITATIVE MEASURE OF STRONG PITCH-ANGLE ANISOTROPIES D. K. Haggerty (1), E. C. Roelof (1) (1) The Johns Hopkins University Applied Physics Laboratory firstname.lastname@example.org Energetic particle time histories and angular distributions are used to probe both local and distant structures and acceleration mechanisms throughout the heliosphere. Anisotropies observed in near-relativistic solar electron events can indicate the duration of particle acceleration and give insight to the acceleration mechanism. The observation of unidirectional or bidirectional anisotropies in magnetic clouds at 1 AU can give insight into the global structure of the internal flux rope through which the energetic particles propagate. Here we detail a quantitative method to measure the strong anisotropy of energetic particle distributions. The pitch-angle anisotropy is characterized in the frame moving with the solar wind by a piecewise exponential function j = j0exp() where is the anisotropy measure and is the pitch cosine. Plasma flow velocities are required for ion anisotropy calculations (because of connection effects), but not for near relativistic electrons. The simplicity of implementing this method, coupled with error estimates for both Poisson counting fluctuations and root-mean-square deviations of the sector intensities from the optimal fit values, makes this a robust and effective tool for the analysis of energetic particle observations.