The North American leafminers recorded from hosts in Onagraceae are summarized. The immature stages of Aristotelia isopelta Meyrick (Gelechiidae) are reported for the first time; larvae feed on Oenothera biennis L. and Epilobium sp. and are parasitized by Chelonus (Microchelonus) Szépligeti (Braconidae). Mompha argentimaculella (Murtfeldt) (Momphidae) is newly recorded from O. pilosella Raf. and is parasitized by Pnigalio flavipes (Ashmead) (Eulophidae). Mompha locupletella (Denis and Schiffermüller) is newly recorded from North America, mining leaves of E. ciliatum Raf. and parasitized by Sympiesis argenticoxae Girault (Eulophidae). New observations of the larval habits of the Circaea L. miner M. terminella (Westwood) are reported, along with the rearing of a parasitoid, Microgaster n. sp. (Braconidae). Distribution data are summarized for the Chamerion angustifolium (L.) Holub miner Mompha raschkiella (Zeller), whose presence in North America was only recently discovered. Numerous other Onagraceae-feeding Mompha species from the western U.S.A. have yet to be documented.