Distribution and host records are summarized for the three groups that comprise nearly all Nearctic leaf-mining muscoid flies. Chirosia Róndani (Anthomyiidae) includes 18 species in the USA and Canada; as far as is known all are fern feeders. The confirmed leafminers are in the C. flavipennis section, with members of other groups boring in rachises or forming galls. Pegomya s. str. (Anthomyiidae) includes 45 Nearctic species, primarily with hosts in the Caryophyllales (Amaranthaceae, Caryophyllaceae, Polygonaceae), but with others on Asteraceae, Fabaceae, Polemoniaceae, and Solanaceae. Larvae in this subgenus are all believed to be leafminers, although P. atlanis Huckett may be a stem borer. Eleven species of Delininae (Scathophagidae) occur in North America, and the five that have been reared are all leafminers of monocots (Asparagaceae, Melanthiaceae, Orchidaceae). New rearing records and other observations of immature stages are presented for each of these groups.