Hand washing prevents the transmission of infections including waterborne, parasitic and nosocomial infections. Hand washing is the most effective and cheaper method of preventing the spread of germs. The main aim of the study is to evaluate the knowledge, attitude, behavior and practice of hand washing among the heterogeneous population including Doctors, Nurses, Medical students, Paramedical staffs, Non-Medical students, School children and mothers of under-five in Tiruchirappalli, Tamilnadu. Method of study is cross-sectional study, study conducted for 2 months from June-August 2015. Among the 400 participants, 10% doctors, 7.5% nurses, 25% medical students, 7.5% Para-medical staffs, 25% Nonmedical students, 12.5% school children and 12.5% mothers of under-five were participated. The data were analyzed and found that the knowledge among doctors, nurses, medical students, Para-medical staffs, Non-medical students, school children and mothers was 64.5%, 58.8%, 50.7%, 57.6%, 38.28%, 49.3% and 39.5% respectively. The attitude among doc