Fullerene nanoparticles have potential uses in a variety of applications including pharmaceuticals, lubricants, composite materials, specialized coatings, and interfacing membrane surfaces. In this study, the supercritical antisolvent process is used to reduce fullerene particle size from 40 mu m to as low as 29 nm. C-60 dissolved in toluene is injected into supercritical CO2, causing precipitation of C-60 as fine particles. Because of the high diffusivity of CO2 in toluene, a rapid supersaturation is achieved, which results in the formation of C-60 nanoparticles with a narrow size distribution. The effect of pressure, temperature, and jet velocity on particle size and morphology is studied. The particle size increases linearly with the density of supercritical CO2. A high jet velocity yields spherical particles whereas a lower jet velocity yields both spherical and rodlike particles. In most cases, a uniform thin film of the particles is obtained on the collection plate.