During the Voyager 2 flyby of Neptune the planetary radio astronomy (PRA) experiment recorded an intense noise near the equatorial plane around 3.4 and 4.2 RN, as already observed during previous Voyager ring plane crossings at Saturn and Uranus. This noise is interpreted as being due to impact ionization of dust grains striking the spacecraft. We deduce a power law index of the grain mass distribution of about 2. The PRA system is sensitive to particle with radii larger than ≂1.6 &mgr;m, and the largest particles, detected near the ring plane, are evaluated to have a radius of ~10 &mgr;m. The spatial dust distribution along the spacecraft trajectory around the two equatorial crossings is found not be be symmetrical with respect to the ring plane and spread over wide regions: over ~2 RN perpendicularly to the equatorial plane with the densest part concentrated within ~700 km. The vertical optical depth &tgr; of this dense region is found to be 10-6--101-8. ¿American Geophysical Union 1991