Mixing liquids on the micro-scale is difficult because the low Reynolds numbers in microchannels and in microreactors prohibit the use of conventional mixing techniques based on mechanical stirring which induces turbulence. Static mixers can be used to solve this mixing problem. In this paper, micromixers having geometries very close to those of conventional large-scale static mixers used in the chemical and food-processing industry are presented. Two kind of geometries have been studied. The first type of mixers is composed of a series of stationary rigid elements that form intersecting channels to split, rearrange and combine component streams. The second type of geometry is composed of a series of short helix elements arranged in pairs; each pair comprised of a right-handed and left-handed element arranged alternately in a pipe. Micromixers of both types have been designed by CAD and manufactured with the integral microstereolithography process, a new microfabrication technique that enables the manufacturing of complex, three-dimensional objects in polymers. The realized structures have been tested experimentally. Numerical simulations of the micromixers with the CFD program Fluent(TM) have been performed to evaluate their mixing efficiency.