We conducted a prospective study of 459 women to determine if a one-session class in breast self-examination (BSE) can improve competence and frequency. Women who attended the class were randomly assigned to one of two groups. We assessed three areas of competence of BSE in one group immediately before the class, in the other group immediately after the class, and in both groups at follow-up one year later. Of the 459 women who attended the class, 286 returned for the one-year follow-up. All three areas of competence measured showed significant improvement in the group tested immediately after the class compared with the group tested just before the class. Competence scores at the one-year follow-up remained twice as high as those before the class although there was a decrease in competence from just after the class. Younger women proved more competent in performing BSE than did older women. At one year, participants further reported performing BSE nearly twice as often as before the class. We conclude that competent BSE can be learned and frequency of BSE can be increased from a one-session class.