  The production of mesons in nucleon-nucleon collisions is reviewed from the
viewpoint of the meson-exchange picture. In the first part various possible
production mechanisms and their relative importance are discussed. In addition,
general features of meson production are described.
  In the second part special emphasis is put on pion production. Implications
of chiral perturbation theory are discussed. Results based on a specific
meson-exchange model for pion production in nucleon-nucleon collisions are
presented. The model is utilized to calculate several spin-dependent
observables of the reactions $pp \to pp\pi^0$ and $pp \to pn\pi^+$ such as
spin-correlation parameters. This allows us to study the role of the Delta
resonance at close to threshold energies.
  The talk closes with a brief discussion of the production of $\phi$ mesons as
an example for the production of heavier mesons. A strategy is outlined that
allows to extract information on the structure of the nucleon from the reaction
$NN \to NN \phi$.
