The primary focus of this project has been the ethnobotany of medicinal plants used on the north coast of Peru. Northern Peru represents the “health axis” of the old Central Andean cultural area stretching from Ecuador to Bolivia. The traditional use of medicinal plants in this region, which encompasses in particular the Departments of Piura, Lambayeque, La Libertad, Cajamarca, Amazonas, and San Martin possibly dates as far back as the first millennium B.C. (north coastal Cupisnique culture) or at least to the Moche period (A.D. 100-800), with healing scenes and healers frequently depicted in ceramics. Precedents for this study have been established by the late 17th-century plant collections of Bishop Baltasar Jaime Martínez Compañón [14], ethnoarchaeological analysis of the psychedelic San Pedro cactus [15], curandera depictions in Moche ceramics [16], and research on the medicinal plants of Southern Ecuador [17, 18] used in a field guide on the medicinal plants of the region [19]. Fieldwork for the present study started in the markets of Trujillo (Mayorista and Hermelindas) and Chiclayo (Modelo and Moshoqueque) in 2001. In the present book we provide of the North Peruvian data and illustrations from our ethnobotanical database (www.olorien. org/ebDB) of 510 medicinal plants organized under the headings: scientific name, vernacular name, plant parts used, administration, preparation, use, and collection number