Microrheology can be used for high-throughput screening of the rheological properties of sample libraries of complex fluids. Two passive techniques are particularly suitable: video microscopy and diffusing-wave spectroscopy. The techniques complement each other very well and can be applied to samples that offer different experimental challenges. We offer a thorough analysis of the strengths and limitations of microrheology with the emphasis on high-throughput applications. To illustrate the potential of microrheology, results are presented for two representative cases: the rheological screening of aqueous solutions of a block copolypeptide library and the rheological phase diagram of a water/surfactant/salt system. (C) 2003 Kluwer Academic Publishers.