Use of medicinal plants has long been popular among Iranian people.Conversion of unwritten medicinal plants' encyclopedia to a written source is the main purpose of writing this book, because original information's protection of region's medicinal plants and preventing destruction of valuable information is very important and can be used by researchers in future to scientifically document their uses. In this regard this book is providing a written information of indigenous knowledge from southern areas of Ilam province in south of Iran which is a valuable source for medicinal plants.Ilam province, known as the "thyme land" or "the rising sun land" and "bride of the zagros mountains", is located in a special situation in west of Iran. The first chapter of the book is an introduction to medicinal plants. The second chapter introduces Ilam and its social historical and cultural status. In the third chapter traditional effects of herbal plants and used organs of medicinal plants of the region are presented.