"Background: Malnutrition and infectious diseases both occur in the same unfortunate children and together they play a major role in causing the high morbidity and mortality in them. Out of all the childhood illnesses, acute respiratory tract infections, diarrhoeal diseases and malnutrition are the principle causes of illness and death in the developing countries. Acute Diarrhoeal diseases (ADD’s) are reported to be the 2nd leading cause of child morbidity and mortality. Objectives: To study the attack rate of Acute Diarrhoeal Disease among pre-school children and to study the socio-demographic variables of pre-school children suffering from Acute Diarrhoeal Disease. Methods: A Longitudinal study was conducted among preschool children (3-5years) who were selected from Private pre-primary school of urban area and followed for the period of one year. Mother/guardian/teacher was interviewed by using pre-tested proforma during this period. Results: About 56% of children found suffering from ADD with 0.6 episodes per children per year among private pre-primary school. Higher proportions of ADD affected children were residing in nuclear type of family, belonging to middle socio-economic class, mothers were literate & housewives, born with order >2 compared to non ADD affected children. Conclusion: Maximum number of children from private pre-primary schools suffered with nearly one attack of Acute Diarrhoeal Disease with maternal illiteracy and working mothers found favorable factors. Immunization coverage, EBF and proper weaning play a very important role in prevention of infections."