Species composition, abundance, and vertical distribution of the stomiid fish assemblage were investigated in the eastern Gulf of Mexico, a low-latitude, oligotrophic oceanic ecosystem. Seventy-two described species, representing 18 genera, and one undescribed species were identified from 1155 trawl samples. With an additional 10 species reported elsewhere, the stomiid species number now known equals 83, making the Stomiidae the most diverse fish family in the Gulf of Mexico. The assemblage was dominated by three species,Photostomias guernei, Chauliodus sloani and Stomias affinis. These species, as well as four other common species, exhibited an asynchronous diel vertical migration pattern (450–900 m during day; 20–300, 550–900 m at night). The percentage of the populations of the three dominant species migrating daily ranged from 50–70%. Two other patterns occurred in less abundant species: synchronous migration (400–700 m during the day, 0–200 m at night); and, possible migration from the bathypelagial (> 1000 m during day; 50–300 m at night). Minimum abundance and biomass estimates for the entire assemblage were 1.86 × 105 individuals and 35.3 kg DW•km-2 in the upper 1000 m. Stomiids comprised approximately 10% of the micronekton standing stock in the eastern Gulf. Extrapolating eastern Gulf data to the world warm-water mesopelagial, abundance results suggest that stomiids are the dominant mesopelagic upper-trophic level predatory fishes, and as such may serve as key trophic mediators in the transfer of energy in these ecosystems.