In two companion papers this week, researchers from the Whitehead Institute Center for Genome Research report important findings that set the stage for the next steps in the Human Genome Project—mapping and identifying all the genes that predispose us to common diseases. The studies, one by Mark Daly, Eric Lander, and colleagues, and the other by John Rioux and colleagues at Whitehead Genome Center, provide the impetus for building a “haplotype” map of the genome—a map that will make it easier, faster, and perhaps cheaper to find disease-causing or disease-predisposing genes.