A survey of the medicinal and poisonous plant diversity in the flora of the Carirí of the State of Paraíba, Brazil, has been made. Medicinal and poisonous properties of 121 plant species belonging to 96 genera and 45 families were recorded. Of these, 119 species belonging 44 families, representing about 98% of the total, are used for medicinal purposes, and five species are considered as poisonous. The Fabaceae (Leguminosae) family has the highest number (16) of medicinal plants diversity in the area, followed by 11 species of Asteraceae and 9 of Solanaceae. Information on these 121 species are presented together with their medicinal uses. This study aims at emphasizing the importance of setting up conservation priorities, and sustained development of various medicinal plants of semi-arid area of Northeast of Brazil.