Human DNA has been identified successfully from several hematophagous and necrophagous insects. Because bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), imbibe human blood and achieve high population densities in human habitations, we assessed the stability of human DNA in bed bugs over time and matched blood isolated from bed bugs to an individual human host. Using polymorphic autosomal short tandem repeat (STR) markers commonly employed in forensic investigations and an Alu insertion polymorphism, we unambiguously identified human DNA in bed bugs up to 48 h after blood ingestion and visualized faint bands from bed bugs fed 72 h prior. Using STR markers, we could not identify human DNA in bed bug excreta at any time point after blood ingestion. All blood samples matched identical STRs amplified from the host that the bed bugs had fed on, indicating the feasibility of this approach to identify a human host within 48–72 h of blood ingestion.