Loop calculations and OZI rule

The role of two step mechanisms in the OZI rule violation in N (N) over bar annihilation at low energies is reviewed. The full calculation of two-meso n doorway mechanisms shows that the off-mass-shell contributions are import ant. Moreover, for the phi pi(o) and phi rho annihilation channels three-me son doorway contributions are non-negligible and improve agreement with the data. A significant enhancement of phi, production is found in the resonan t rescattering mechanisms (p) over bar p --> pi(+)pi(-)K (K) over bar pi(+) pi(-)phi and (p) over bar p -->eta K (K) over bar --> eta phi.