A description of the interplanetary meteoroid environment is proposed in terms of distinct populations, each of which has separable distributions in particle mass and in orbital inclination, eccentricity, and perihelion distance. This treatment leads to expressions for particle concentration and flux which explicitly incorporate both Keplerian dynamics in heliocentric orbit and the directional properties of particle impact velocities for a spacecraft detector. Data which represent radar meteors, the zodiacal light, and fluxes from impact detectors abroad the Pioneer 10 and 11, Helios 1, Galileo, and Ulysses spacecraft have been combined with the interplanetary flux near Earth (from lunar crater counts and orbiting spacecraft) to evaluate parameter values for the mass and orbital distributions. Five distinct meteoroid populations are needed to successfully match all the data, and they span the ranges from 10-18 to 1.0 g in mass and from <0.1 to 20 AU in heliocentric distance. The five populations, each named for a distinctive characteristic of their orbital distributions, and in increasing order of mean particle mass, carry the labels eccentric, inclined, halo, core, and asteroidal. ¿ American Geophysical Union 1992