Specific insect DNA fragments were amplified using the polymerase chain reaction (PCR), followed by direct DNA sequencing of the amplification products. A total of 2,300 base pairs of mitochondrial DNA were sequenced from each of three blowfly species; all three species are important in forensic entomology, because they lay their eggs at predictable times in the decay cycle of a corpse. Results revealed 118, 186, and 196 differences between the sequences of different pairs of the three species. These abundant DNA sequence differences make it possible to clearly identify the immature larval stages of these insects. These DNA sequence differences were also used to predict species- specific, diagnostic restriction sites in the amplified DNA; these predictions were verified by digestion with nine restriction enzymes. Figures, table, appended DNA sequences, and 20 references (Author abstract modified)