Anticipating the full revision of the New World genus Orthosia Decaisne (Asclepiadeae, Orthosiinae), the following new combinations for 14 taxa formerly placed in Amphistelma Grisebach, Cynanchum L., Metastelma R. Brown, Tassadia Decaisne, and Vincetoxicum Wolf are provided: Orthosia bonplandiana (Roemer & Schultes) Liede & Meve, O. calycina (Schlechter) Liede & Meve, O. cardozoi (Morillo) Liede & Meve, O. cassythoides (Suessenguth) Liede & Meve, O. ellemannii (Morillo) Liede & Meve, O. guilleminiana (Decaisne) Liede & Meve, O. henriqueana (Silveira) Liede & Meve, O. meridensis (Morillo) Liede & Meve, O. parviflora (E. Fournier) Liede & Meve, O. pearcei (Rusby) Liede & Meve, O. pubescens (Greenman) Liede & Meve, O. scoparia (Nuttall) Liede & Meve, O. selloana (E. Fournier) Liede & Meve, and O. stannardii (Morillo) Liede & Meve. Full and comprehensive synonymies for O. scoparia and O. guilleminiana are given to preclude the confusing use of many different names for these widely distributed species. Lectotypification for 14 taxa is presented: Amphistelma ephedroides Grisebach, A. filiforme Grisebach, A. riedelii E. Fournier, A. selloanum E. Fournier, Astephanus pubescens Greenman, Cynanchum bonplandianum Roemer & Schultes, C. trilobulatum Lillo, Metastelma angustifolium Turczaninow, M. atrorubens Schlechter, M. calycinum Schlechter, M. fawcettii Schlechter, M. peruvianum Schlechter, M. rariflorum Schlechter, and M. retinaculatum Schlechter. Orthosia woodii Meve & Liede, a new endemic species from Bolivia, is described and illustrated.