For use of comparative material used in the preparation of this paper, I am indebted to Richard J. Baldauf, Texas Cooperative Wildlife Collection (TCWC); Charles M. Bogert, American Museum of Natural History (AMNH); James A. Peters, United States National Museum (USNM); Hobart M. Smith, University of Illinois Museum of Natural History (UIMNH); Charles F. Walker, University of Michigan Museum of Zoology (UMMZ); and Ernest E. Williams, Museum of Comparative Zoology (MCZ). KU refers to the University of Kansas Museum of Natural History. I am especially grateful for help in obtaining specimens and data to Linda Trueb, who accompanied me throughout Mexico and Central America, where we were joined by John D. Lynch in Costa Rica and Charles W. Myers in Panama. Linda Trueb offered helpful suggestions in the course of preparing the manuscript, and David M. Dennis skillfully prepared the illustrations which more accurately depict the frogs than my written descriptions; both of these persons have my thanks for their contributions. Ratibor Hartmann of Finca Santa Clara, Chiriqui, Panama, made possible our travels to the Rio Changena on the Atlantic slopes of Bocas del Toro. Field work in Costa Rica was facilitated by the Organization of Tropical Studies through the courtesy of Stephen B. Preston and Norman Scott. Rodolfo Hernandez Corzo of the Direccion General de la Fauna Silvestre provided the necessary permits to collect in Mexico. I thank each of these persons for his helpfulness and cooperation. Field work in Mexico and Central America and the associated laboratory studies on Middle American hylid frogs are supported by grants from the National Science Foundation (GB-1441 and GB-5818). The field work in Panama was part of a survey of the herpetofauna of that country carried out in cooperation with the Gorgas Memorial Laboratory and supported by the National Institutes of Health (GM-12020). Hyla xanthosticta new species Plate 17 _Holotype._--Adult female, KU 103772, from the south fork of the Rio Las Vueltas on the south slope of Volcan Barba, near the northwest base of Cerro Chompipe, Heredia Province, Costa Rica, elevation 2100 meters; obtained on June 26, 1966, by John D. Lynch. _Diagnosis._--A member of the _Hyla pictipes_ group (Starrett, 1966), characterized by having dorsum uniform green, canthal stripe bronze-color, flanks and anterior and posterior surfaces of thighs dark brown with bright yellow spots, throat and belly yellow, and hands having only vestigial web.