  We report results from a search for stable particles with charge > $10^{-5}$
e in bulk matter using levitated dielectric microspheres in high vacuum. No
evidence for such particles was found in a total sample of 1.4 ng, providing an
upper limit on the abundance per nucleon of 2.5 x $10^{-14}$ at the 95%
confidence level for the material tested. These results provide the first
direct search for single particles with charge < 0.1 e bound in macroscopic
quantities of matter and demonstrate the ability to perform sensitive force
measurements using optically levitated microspheres in vacuum.
