The multipoint identity-by-descent method (MIM) was used to analyze simulated data for quantitative traits from GAW9. A two-stage method of implementation was used. First, polymorphic markers spaced 6-12 cM apart were used to identify chromosomes of interest for each trait Q1-Q4; and second, for each of these chromosomes, markers spaced 2 cM apart were used to confirm the linkage detected and refine the region for the susceptibility loci. MIM performed well at both levels of mapping, correctly detecting major genes for trait Q3 on chromosome 2, trait Q2 on chromosome 1, and trait Q4 on chromosome 5. © 1995 Wiley-Liss, Inc.