Objectives : The purpose of this descriptive study was to provide basic data for developing an effective breast feeding program through investigating the level of knowledge, attitude and practice rate on breast feeding according to the infants' age. Methods : The subjects were 116 mothers whose infants were 1~12 months old. The data were collected from October 1 to December 31, 2002, using mail questionnaires and were analyzed by using the SPSS program with frequency, mean, χ²-test, t-test, ANOVA, and the Pearson Correlation Coefficient. Results : The average practice rate of breast feeding in the 1st month was 61.7%, however it decreased to 13.8% in the 6th month. The major reasons for interrupting breast feeding were insufficient breast milk 49.1% and job 19.3%. There was no significant difference found in the mother's knowledge level of breast feeding according to type of feeding at any age of infant. There was significant difference found in the mother's attitude toward breast feeding according to type of feeding in the 1st month(F=4.011, p<0.05). There was no significant correlation between the mother's knowledge level of breast feeding and type of feeding at any age of infant. There was significant correlation between the mother's attitude toward breast feeding and type of feeding in the 1st month(r=0.246, p<0.01). Type of feeding differed according to personal breast feeding experience and breast feeding education experience. Conclusions : It is recommended to develope new strategies to improve the breast feeding rate 1 month after birth, such as assistance to solve some difficulties in breast feeding practice and intervention to correct negative attitude toward breast feeding and providing active breast feeding method.