Exotic mesons

A review is given of the current state of searches for, and investigations of, exotic mesonic states in hadronic reactions, $J/\psi$ decays, and $\gamma$, $\gamma$ collisions. These experiments have led in recent years to the discovery of a number of mesonic states whose properties do not fit into the simple quark model of “ordinary” ($\mathrm{q\bar q}$) mesons. The new particles appear to be very serious candidates for exotic hadrons. The current state of the E/iota problem and the nature of the E(1420) meson are discussed.