Flanking recombination events have defined the Huntington Disease gene candidate region to between D4S10 and D4S98, about 2.2Mb. Because of the large size of the candidate region and the likely large number of genes within it we decided to screen cDNA libraries with probes generated from whole Yeast Artificial Chromosomes (YACs) containing parts of this region. We have thus far used 4 YACs ranging in size from 180kb to 600kb covering 880kb and have isolate 13 cDNA clones, 7 of which are unique. Three of the 13 clones contain parts of the 3' untranslated region of the alpha-adducin gene. One YAC of 600kb could not be purified from two yeast chromosomes, therefore this YAC probe had a net complexity of 1.8Mb. Even so this probe identified a cDNA from the HD candidate region indicating that very large YACs may be used as probes.