The purpose of present study was to identify the effect of 4 month breast feeding promotion program implemented in may 1995 on the changes in confidence towards the breast feeding practice over the first month of postpartum. A quasi-experimental design was used to examine the effect of prenatal breast feeding education and postpartum nursing intervention program between the groups of women who were seen at a university hospital Obstestic clinic(experimental group, n=89) and those who received prenatal care at a medical center(control group, n=99). In data collection, interview or telephone survey technique was utilized at 32 or more weeks of gestation and at one week and one month after childbirth. The study results are as follows: 1. No significant difference was noted in the breast feeding confidence scores between the experimental and control groups(P=0.393), but there was a significant difference between three points of time before and after childbirth(P=0.0001). However, an interaction between repeated measures of the confidence score and implementation and non-implementation of breast feeding promotion program was present(P=0.000), that is, the pattern of confidence score changed differently between groups and no program effect was obtained. 2. Among control group mothers, a similar result was noted as above between the breast feeding and non-breast feeding groups. 3. Among the mothers participated in the breast feeding promotion program, no group difference was demonstrated in the confidence scores between the breast feeding and non-breast feeding groups(P=0.0603), but with a significant time difference(P=0.0006). And no interaction was present between time and group(P=0.1532). There was no statistical significance between groups but the confidence scores of the breast feeding group remained higher than those of the non-breast feeding group at all three points of time. Conclusively, a tendency for confidence buildup was revealed by maintaining a steady level of confidence score at all three points of time among breast feeding mothers who participated in the program and the ones who did not as well, whereas no such tendency was noted in the non-breast feeding group. Thus, confidence towards breast feeding needs to be interpreted in the maintenance of an adequate level of confidence rather than an increase; at large. The study findings indicate that culturally adjusted factors influencing breast feeding practice, especially during the first month of postpartum need to be thoroughly analyzed associated with qualitative research effort on feelings and experiences of breast feeding mothers for the development of more practical and active nursing intervention program.