Pions in hadron physics

The Julich model for pion production in nucleon-nucleon collisions is revie wed. First calculations for recently measured spin correlation coefficients are presented. The influence of resonant [via the excitation of the Delta (1232)] and nonresonant p-wave pion production mechanisms on these observab les is examined. In the second part of the talk we discuss the role of pion s in the (d) over bar-(u) over bar -asymmetry of the nucleon sea and its co nnection with the inclusive production of forward neutrons. We compare pred ictions for the pion structure function at small x with the data extracted from deep inelastic forward neutron production.