The use of fluorescent end-labeled primers has proved successful for rapid, semiautomated genotyping of microsatellite loci. However, custom synthesis is expensive and costs can be prohibitive when a wide range of markers is to be analyzed for only a few genotypings. This particularly applies to high-resolution genetic mapping in the mouse either in the construction of global maps or in the production of local high-resolution genetic maps for positional cloning. We demonstrate here the use of fluorescent dUTPs for cost-effective, high-throughput microsatellite genotyping in the mouse. This alternative to the use of fluorescent end-labeled primers for semiautomated genotyping is potentially applicable to the construction of linkage maps in other species.