Koutrolikos, KonstantinosSuperspace techniques are used to construct lagrangians in terms of unconstrained prepotentials, that describe arbitrary superhelicity irreducible representations of the 4D, N=1 super-Poincaré group. We study the component structure of all these theories and extract the corresponding component lagrangian for each one of them. Furthermore we provide explicit expressions for the transformation of the components under supersymmetry. The counting of the off-shell degrees of freedom will provide useful information for the possible higher N representations. For the case of massive representations, we provide new superspace lagrangians for massive gravitino (superspin 1) and for the massive extension of non-minimal supergravity (superspin 3/2). The superspace lagrangian for supergravity will shed some light to the structure of the auxiliary superfields that are required for the construction of higher superspin theories.enDissertationTheoretical physicsPhysicsrepresentationssuperhelicitysuper poincaresuperspinsupersymmetry