In my more than 30 years of experience in teaching medical and health statistics at all levels, no other book was found more useful for medical under and postgraduate students and research workers (Hindi/English) so simple, brief yet comprehensive, beautifully written elaborating with practicable examples relating to medical and health practices. Dr Ramchandran, Head of Statistical Department, AIIMS, New Delhi, Dr Mahajan by writing so simple a book on Biostatistics has raised the status of biostatistics as a science so also of a teacher of statistics in various medical colleges. It has changed the outlook of medicos in practical application of this science in solving their problems, in writing thesis and research papers. Dr BN Tandon, Professor and Head, Gastroenterology Department, AIIMS, New Delhi, Dr Mahajan has successfully served the needs of medical students by updating of demography and application in medical practice and research resulting in wide circulation. Dr SS Srivastava, Director General, Central Statistical Organization, Government of India, New Delhi, Dr Mahajan has done a yeoman service in practice of biostatistics as a science in medical and health sciences and so also as the Statistician Consultant in Biostatistics.