Many investigators need to determine whether individuals belong to the same species. DNA-sequence data have helped with this task, but current procedures of DNA isolation from millimeter-scale crustaceans, such as harpacticoid copepods, leave little to no voucher material for morphological analysis, and many procedures yield only enough DNA for a single amplification reaction. We therefore developed a DNA-isolation procedure that yielded essentially intact exoskeletons and sufficient DNA for multiple polymerase chain reactions.DNA-amplification success of our DNA-isolation procedure was relatively insensitive to (1) the length of preservation time from sample collection to DNA isolations and (2) the length of time the DNA was stored at −20°C after isolation. An additional benefit of our procedure is therefore that the DNA isolated is relatively stable.Primers available for the nuclear 18S rRNA gene and the mitochondrial cytochrome oxidase b (cytb) gene are known not to work for many harpacticoids. We therefore designed primers that would amplify and sequence an ~750-base-pair fragment of the 18S rRNA gene and others that would amplify and sequence an ~450-base-pair fragment of the cytb gene. Both primer sets worked for at least 12 harpacticoid families.