The traditional view has been that all species of the phylum Ctenophora are capable of producing light. Our inability to elicit luminescence from members of the well-known genus Pleurobrachia, as well as a lack of published documentation, led to an effort to determine whether this genus is truly bioluminescent. Physical and chemical assays of several species from the family Pleurobrachiidae produced no evidence of bioluminescence capability, although all other species of ctenophores tested gave positive results. Some of the historical misperception that Pleurobrachia can produce light might be attributable to confusion with similar luminous genera.