Japanese cedar, Cryptomeria japonica (Thunb. ex L.f.) D. Don [Cupressaceae Bartling, formerly assigned to Taxodiaceae Warm.] is increasing in popularity as a landscape plant in the eastern United States. A taxonomic study of cultivars grown in the eastern United States was conducted. Forty-five cultivars were recognized. Each cultivar bears synonymy, a quantitative morphological description newly described from field data, herbarium vouchers, references to original literature and observational notes. A glossary of taxonomic terms relevant to Cryptomeria is presented. A taxonomic key is presented for segregation of cultivars that should assist professional plantsmen in identification of taxa cultivated in the eastern United States.