OBJECTIVE Breast cancer is one of the most important problems of public health and education regarding breast self-examination is one of the important steps for identifying breast tumors at an early stage. The present study was carried out to assess knowledge, attitude, and practice of breast self-examination among patients attending health centers. METHODS In a KAP (Knowledge, Attitude and Practice) survey 663 women of 13 randomly selected municipal health centers were interviewed. The number of interviews in each health center was proportional to the mean number of women seen per month. In the data analysis, women's answers for knowledge, attitude and practice regarding breast self-examination were classified according to their adequacy as previously defined. Adequacy was compared among categories of control variables with Chi2 test. RESULTS The results showed that knowledge and practice of breast self-examination were adequate in 7.4% and 16.7%, respectively. However, attitude was adequate in 95.9% of the women interviewed. The study also showed that 58.1% of the women interviewed referred that forgetfulness was the main barrier for not performing self-examination. CONCLUSIONS Women attending the health centers sampled in this study had inadequate knowledge and practice about breast self-examination but they had an adequate and favorable attitude about it.