Relates the shape of the retarding potential curve produced by gridded electrostatic analyzers to the floating potential, the kinetic temperature, and the half-angle subtended in velocity space by the particles. Special emphasis is placed on the case in which the particles are Maxwellianized but restricted within a 'loss cone' in velocity space of half-angle phi ₀. The cases of pulsed and steady-state supply of particles are both considered. By using an appropriate computer program to compare the analytical expressions derived herein with experimental retarding potential curves, one may obtain significantly more information about the velocity distribution than is possible with conventional methods of data reduction. A series of illustrative experimental runs is reduced with a computer program, and the magnitude of run-to-run variations is discussed.