Results suggest that the number of serial murder victims has been underreported; in any given year hundreds of additional serial killer victims could be added to existing counts by using data on missing persons who are actually dead, the missing missing who are dead (unreported missing prostitutes and foster children), the unidentified dead who were murdered by serial killers, and serial murder victims from institutional settings (nursing homes, hospitals, and prisons) who were misclassified as natural deaths. The present research suggests that even if a small proportion of these deaths were serial homicides then the true serial murder victim counts are and always have been low. By counting potentially hidden serial murder victims, a minimum number of 182 annual serial murder deaths and as many as 1,832 uncounted annual serial murder deaths could be added to existing counts. In addition to providing lower and upper estimates of possible victims from these sources, this article also provides a methodology for counting “the missing missing”, missing persons who were never reported as missing and some of whom may be serial murder victims. Research indicates that although early attempts to estimate the number of serial murder victims in the United States varied greatly and were exaggerated (in the 1980s), current estimates might actually underestimate the number of serial murder victims. The limited resources to combat homicide and serial homicide, the horrific loss of life, the fear engendered by serial murder, and the high cost of investigations make it critically important to establish reliable estimates of risks for certain populations. The present research suggests a paradigm shift in which missing persons cases and marginalized victims are prioritized rather than minimized, and in the future will be necessary to effectively address this crime. Table, notes, references