Objective: 1 To determine frequency of mothers who are not exclusive breast feeding. 2 To determine factors preventing to not exclusively breast feeding in infants (0-6 month) presenting to tertiary care hospitals. Study design: Cross sectional Descriptive Place and duration of study: Study was performed in Children Hospital Chandka Medical College Larkana and Ghulam Muhammad Mahar Medical College Hospital Sukkur from January 2009 to June 2009. Patient and Methods: This is a prospective, a cross sectional descriptive study, including 100 breast feeding mothers (0-6 month age), and to determine the frequency of not exclusive breast feeding and the factors preventing to not exclusive breast feeding. Results: Exclusive breast feeding in tertiary care hospitals is 20% and factors preventing from exclusive breast feeding were, working mother 40%, to familiarize baby to bottle feeding 22.5%, perceived insufficient milk 17.5%, real insufficient milk 7.5%, parental pressure 3.75%, and preterm babies 3.75%, and Cesarean delivery 2.5%, lactation failure 1.25%, and next pregnancy 1.25% Conclusion: Exclusive breast feeding is 20% in mothers. Mostly mothers use to give mixed feeding and small percentage gives exclusive bottle feeding. Most common factors associated with failure of exclusive breast feeding are working mother, false insufficient milk, to familiarize baby to bottle feeding by working mother. Among less common factors are true insufficient milk, preterm babies, parental pressure, lactation failure, caesarean section delivery and next pregnancy.