Problem 1 was designed to involve an oligogenic model with four “disease susceptibility” loci, such that all individuals with at least four “upper-case” alleles were at equal risk to be affected (and those with three or fewer were not at risk). Two of these loci were identical to marker loci, thus giving rise to weak disease-marker associations. The other two were located between marker loci, with no linkage disequilibrium. Participants were given 200 nuclear families with at least one affected child, along with 100 control families with no affected individuals. The first two loci were intended to be detectable via association analysis. The remaining two loci were virtually undetectable in this data set. ©1995 Wiley-Liss, Inc.