On page 78, Zhou et al. describe a technique for scoring loss of heterozygosity in tumors. They used fluorescent molecular beacons and “digital PCR” to detect SNP loci for which the patient was heterozygous, and applied likelihood techniques to ask whether the markers were lost through allelic loss in tumors of 70 patients. The technique is reproducible enough to allow correlation of chromosome loss with an important biological property of tumors—vascular invasion.