The ABI PRISM (®) 377 DNA Sequencer is used for a variety of microsatellite-based research. The platform provides researchers with a cost-effective means for high-throughput genotyping, which can be further optimized by multiplexing microsatellite loci or by using a tail-labeling approach to screen large sets of markers. The goals of this chapter are to present a protocol for performing microsatellite-based analyses on the ABI 377 and to provide researchers with information on how to troubleshoot common issues associated with running the ABI 377 sequencers.