Species of the trichoniscid genus, Miktoniscus Kesselyak, from the New World are reviewed. Two of them, M. halophilus Blake and M. medcofi (Van Name), are redescribed and are the principal species in eastern United States. M. halophilus is present along the E coast from Massachusetts to North Carolina. It inhabits coastal reed grass swamps and nearby locations. In North Carolina it is present inland to Durham in leaf litter in deciduous forests. M. medcofi ranges from W of the Appalachian Mts. to the Mississippi Valley. Frequently, it is present in caves. Most of the species described from local regions within its range are synonyms of M. medcofi. Other species, all from caves, are recognized as discrete species. The presence of M. medcofi in Veracruz, Mexico, is probably correct, but its presence in Rio de Janeiro, Brazil, is questioned. Ecological notes, distribution (map) and population structure data are included for M. halophilus from New Jersey. A new name, M. morganensis n. comb., is proposed for specimens called M. medcofi from a cave in Morgan Co., Alabama.