An examination of the native vascular plant flora of Maryland during 1978 and 1979 as part of a review for the United States Fish and Wildlife Service’s endangered species program disclosed 237 different plants which could be considered rare or endangered in the State. This represents approximately ten percent of the native flora of Maryland. The present paper discusses 74 species, subspecies and varieties of Maryland plants which represent new state records or are plants of extreme rareness. Several species suggested by the Fish and Wildlife Service occur in Maryland, namely Trillium pusillum var. virginianum (E), Alnus maritima (T), Cardamine longii (T), Habenaria flava (T), H. peramoena (T), Juncus caesariensis (T), Lilium grayi (T), Micranthemum micranthemoides (T), and Ptilimnium fluviatile (T). Other recommended species were found in Maryland but were not considered to be in Maryland by the Fish and Wildlife Service at the time; these include such species as Bacopa stragula (E), Isotria medeoloides (E), Lechea maritima var. virginica (E), Panicum aculeatum (T), and Prunus allegheniensis (T). In addition to these species, the Endangered Species Committee of the Smithsonian Institution, and others, suggested additional species be considered as endangered or threatened. For Maryland, these proposed species were Hydrastis canadensis (T), Panax quinquefolium (T), Schwalbea americana (T), and Sida hermaphrodita (no designation as to status proposed). Of the many suggested plants, several can be excluded from Mary land: Alnus maritima (locally common, not threatened); Lilium grayi (not found in Maryland); Bacopa stragula (not a valid species, a synonym of the tropical B. innominata); Lechea maritima var. virginica (locally common and not threatened); Panicum aculeatum (a synonym of the widespread Dichanthelium scabriusculum); and Sida hermaphrodita (local and declining, but populations still widespread). Studies on the Maryland flora supported the proposed listing of the remaining plants as endangered or threatened. Two other plants are now suggested for consideration by the Fish and Wildlife Service: Aster depauperatus, a serpentine endemic of Maryland and Pennsylvania, and Bidens bidentoides var. mariana, a tidal flat endemic restricted to Maryland. Nomenclaturally, Habenaria flava is better considered a member of the genus Platanthera, as is H. peramoena, and we propose to recommend both variants of P. flava, the southern var. flava and the northern var. herbiola, to the Service. We prefer to recognize Hemianthus as distinct from Micranthemum and retain M. micranthemoides in Hemianthus. Errors in author citations noted during the present study include Scleria minor W. Stone, not “(Britton) W. Stone,” and Aster depauperatus Fernald, not “(T. C. Porter) Fernald.” New combinations include Trillium pusillum var. texanum (Buckley) Reveal & Broome, Salix exigua ssp. interior var. angustissima (Andress.) Reveal & Broome, Ptilimnium fluviatile var. viviparum (Rose) Reveal & Broome, Phlox glaberrima var. triflora (Michx.) Reveal & Broome, and Schwalbea americana var. australis (Pennell) Reveal & Broome.