Genome scan linkage mapping projects have identified promising chromosomal locations for AD susceptibility loci, which in some cases have led to discovery of disease-influencing loci. Linkage studies of AD by investigators in the Collaborative Studies on Genetics of Alcoholism (COGA) (Foroud et al. 2000; Reich et al. 1998) and in the intramural program of the National Institute on Alcohol Abuse and Alcoholism (Long et al. 1998) have yielded promising logarithm of odds scores (lod scores; a measure of the likelihood that loci mapping to the region are linked to the disorder under study) for several chromosomal locations influencing risk of AD. Both groups reported that loci influencing risk for AD map close to an alcohol dehydrogenase (ADH) gene cluster on the long arm of chromosome 4. Several other linkage peaks, even ones that did not meet standard criteria for genomewide significance, have led to the identification of likely disease-influencing loci for AD. Analyses of the COGA data set using the transmission disequilibrium test and related family-based methods have revealed several additional areas of interest (Camp and Bansal 1999; Page et al. 1999; Nielsen and Zaykin 1999; Sun et al. 1999).