Many benthic marine invertebrate species have a dispersive larval stage in their life histories. Larvae typically spend hours, weeks, or months developing in plankton before they become competent to settle and metamorphose. Recruitment to benthic populations depends on the numbers of competent larvae transported to sites and/or the interaction between larvae and the surface of substratum. While there is considerable evidence that on large spatial scales, the number of competent larvae transported to sites is determined primarily by hydrodynamics, success of larval settlement on small spatial scales is mediated by biotic and abiotic characteristics of substratum. Larvae of many marine polychaetes require specific cues to settle and metamorphose. Cues can originate from conspecific or congeneric individuals, microbial films, sympatric species, food items, or habitat. Larval settlement in an individual species can be controlled by a single cue or a mixture of cues. Larval settlement of multiple species can be mediated by a common cue or a mixture of cues. Although a variety of chemicals, including proteins, free fatty acids, polysaccharides, inorganic ions, and neurotransmitters, have been suggested as inducing larval settlement of marine polychaetes, few natural cues have been isolated and structurally identified.