A review of quark search experiments

All of the experimental evidence for and against the existence of free, physical quarks from cosmic rays, particle accelerators, and stable matter is reviewed. There is no evidence for the existence of free quarks of fractional charge save for one recent report of niobium pellets of third-integral residual charge. The related searches for quarks of integral charge, for free magnetic monopoles, tachyons, dyons, and other postulated, stable elementary objects are also reviewed. Although some puzzling observations are noted, there is no firm evidence for any of these particles.