A new approach for the realization of true 3D polymer structures is presented in this paper. It consists in adding, in a post-processing microstereolithography step, 3D polymer microstructures on top of a micropart patterned by means of planar processes such as thin films, bulk silicon etching or high aspect ratio structuration (LIGA, RIE, thick resist). In this way, some shape limitations of the planar technologies can be overcome for new functional applications. Moreover, the direct processing of microstereolithography on predefined structures eliminates manipulations which are associated with micro-assembly of separated parts. To demonstrate this combination of microstructuration processes, an example showing a conical axle added by microstereolithography on a SU-8 piece of gearing is presented. (C) 1999 Elsevier Science S.A. All rights reserved.