There appears to be a genetic contribution to the susceptibility to leprosy, and high concordance rates have been observed amongst monozygotic Indian twins. In the April Nature Genetics, Siddiqui et al. report the identification of a major susceptibility locus for leprosy (Nature Genetics 2001, 27:439-441). They performed a genome-wide scan of 245 independent affected sibpairs from Southern India, using 396 highly polymorphic microsatellite markers. Only one region showed a MLS (maximum lod score) or more than 3.0: the marker D10S1661 on chromosome 10p13 has a MLS of 4.09, above the threshold for statistical significance. These results attest to the feasibility of genome-wide linkage studies in the genetic analysis of complex prevalent infectious diseases.