The collection of DNA samples at a crime scene has advanced to the point that a sizable percentage of crime scenes have DNA inadvertently left behind by the perpetrators; however, without a known suspect profile against which to compare the DNA profile from the crime scene, there is no one to include or exclude based on the DNA evidence. With known profiles available for comparison in DNA databases, such as the FBI's CODIS (Combined DNA Index System), many known offenders whose DNA profiles have been stored from their past crimes can be compared with DNA profiles from crimes that have no known suspect. Such a procedure is particularly useful in sexual assault cases, since perpetrators of sexual assault are typically repeat offenders. The size and nature of the DNA database is important. The more suspect samples there are in a database, the greater the chances of obtaining a match. Decisions regarding the size of a DNA database for sexual assault offenders require a cost-benefit analysis, which involves determining the benefits gained from the cost of generating forensic DNA profiles for a database. This article describes the methodology of such an analysis. The analysis determined that the estimated cost to process all of the 366,460 reported sexual assaults per year in the United States is $366 million, an increase of $310 million over the estimated current spending level. The estimated savings that would result from apprehending serial sex offenders early in their criminal careers is a minimum of $12.9 billion. 10 tables, 2 figures, and 59 notes