Efficient and effective whole-genome 10-cM short tandem repeat polymorphism (STRP) scans are now available. Doubling or tripling STRP density to an average spacing of 3-5 cM is readily achievable. However, if typing costs for diallelic polymorphisms can be brought close to, or preferably less than, one-third those of STRPs, then diallelics may gradually supplement or supplant STRPs in whole-genome scans. The power of higher density genome scans for gene map ping by association and for many other research and clinical applications is great. It would be wise to continue investing heavily for many years in genotyping technology.