Abstract. We study the complex structure of the space of vectors and pseudovectors A_ ~ AI@A3 arising from the properties of the Hodge duality in 4-dimensionM spacetimes. This structure appears naturally in the framework of its real Clifford geometric algebra Ceu3 or C~3,1, in which the Hodge duality is the simple multiplication by the volume unit ~. Interpreting the linear combination of a scalar anda pseudoscalar c~ + ~~ asa complex number (A0@A4 --~ C), the odd subspace A_ E C~ is a left/right complex linear space, previously studied by Sobczyk. From the real metric defining C_~, A_ inherits a natural complex bilinear norm N(a). Corresponding to this norm there is the group of complex Lorentz rotations Spinl,3(C), for which we find a formulation using exclusively the real algebra ~. We discuss its behaviour in some examples and find expressions for different decompositions into real and selfdual, real and anti-selfdual, and real and pure imaginary angle rotations. We finally apply our results to the implementation of the rotations corresponding to Euclidean and null signatures inside the real Lorentzian Clifford algebra C 91