We present explicit expressions for general actions of vector and scalar multiplets coupled to N = 2 supergravity. We outline their construction which is based on the superconformal tensor calculus. The vector multiplets may be associated with a gauge group G which may also act on the scalar multiplets. The latter are naturally described in terms of quaternions; in the simplest case their kinetic terms define a nonlinear sigma model of a quaternionic projective space. We give an extension of the vector multiplet action which is not obtained from a chiral superspace density, and contains a Chern-Simons-type term. Transformation rules are given and the conditions for supersymmetry breaking are defined.