Breast self-examination (BSE) is of great potential value for the early detection of breast cancer, especially in areas where mammography and regular examinations by physicians are not practicable. However, BSE cannot be recommended for routine public health practice until there is good evidence that it is effective in reducing mortality from breast cancer. Prospective controlled trials of BSE were therefore initiated in 1985 in Leningrad and Moscow, under the auspices of WHO, in order to establish the value of this potentially cost-effective technique. More than 62 000 women aged 40-64 years have been enrolled in the BSE and control groups in Leningrad and another 88 000 will be added in the next three years. This paper presents the results of the study in Leningrad after the first 15 months.