Interview data from 434 women (aged greater than or equal to 20 years) in two Wellington suburban areas were used to estimate the prevalence and quality of performance of breast self-examination. Although 98% of women were familiar with breast self-examination, and 73% had performed it at least once, only 39% did so at least monthly. Its practice was significantly more common in the middle years (30-59), among Europeans, and in women with tertiary education. Thoroughness or quality of performance was assessed by comparison with Cancer Society recommendations. Scores for examination technique were generally high (mean = 73%) compared with those assessing timing (mean = 47.5%) and conditions under which breast self-examination was performed (mean = 43.3%). Results from this study were compared with 1975-76 New Zealand survey data which produced lower estimates of the prevalence of monthly breast self-examination. Both studies found that more than a quarter of women have never practiced it. Future research and intervention efforts should be directed toward this group of women.