The naturally occurring coumarins are likely to be a large and important group of plant products which are not only metabolic products of the living cells but possess varied physiological and pharmacological actions. Investigations concerning various biological activities of natural coumarins have been undertaken by many investigators in continuing effort. The authors describe on experimental results of biological activities of coumarin derivatives with particular emphasis on 10 different activities that are considered to be of importance in view of the development of new drugs from natural resources.