  In this thesis, we present two aspects of higher-spin gauge field theories:
dualities and interactions. We first consider dualities of the free theories at
the level of the action. Then, external "electric" and "magnetic" sources are
introduced a la Dirac, which leads to a quantization condition on the product
of conserved "electric" and "magnetic" higher-spin charges. In the second part,
higher-spin interactions are studied in the field-antifield (or BRST)
formalism. Theorems are proved about local interactions of sets of exotic
spin-two fields, as well as of sets of symmetric spin-three fields. Some
consistent first-order vertices are obtained.
  The table of contents is as follows. 1.Free higher-spin gauge fields.
2.Spin-s duality. 3.Spin-s electric-magnetic duality. 4.Field-Antifield
Formalism. 5.Interactions for exotic spin-2 fields. 6.Interactions for spin-3
fields.
