Orchids are the highly specialized and diverse plant group with more than 20,000 species distributed throughout the world. The family Orchidaceae is particularly species rich in the humid tropics and sub tropics. Bangladesh is also rich in orchid diversity but no flora or book on orchids of Bangladesh has yet been published. Particularly south east part of Bangladesh is more interesting for its rich plant diversity including orchids. Orchids are not only important for their attractive horticultural value but also important for medicinal properties, ecological diversity and reproductive complexity. An enumeration of the family Orchidaceae in south east Bangladesh and ecological information are provided what can tell us about the quality and health of the habitat. Reproductive characters e.g. many floral characters and factors which might have influence towards pollination and fruiting success have been focused. Conservation aspects are also discussed for saving the orchids in nature. Due to wide diversification, Orchidology today has developed into one of the most dynamic branches of Botany. The book will meet the interest of orchid scientists, enthusiasts and general readers.