Models with more than four quarks

Several models with more than four quarks are reviewed and compared with the four-quark model. They generally have right- and left-handed currents and are of the SU₂ ×{} U₁ type. The lepton sectors are also discussed including the possibilities of heavy charged and neutral leptons. The weak phenomenology, triangle anomalies, degenerate quark masses, and radial excitations are examined.