A computer program is presented for estimating the absolute risk of developing breast cancer over a specified age interval for women with combinations of five risk factors, namely age at menarche, age at first live birth, family history of breast cancer, number of previous breast biopsies, and presence of atypical hyperplasia in biopsy specimens. Statistical methods have been developed and applied to data from the Breast Cancer Detection and Demonstration Project to obtain (i) point estimates of absolute risk by combining relative risk estimates from case-control data and estimated composite incidence rates from cohort data, and (ii) confidence intervals by using implicit delta-method arguments. The program is interactive and easy to use and is therefore well suited to assist in medical counseling. For instance, women with high estimated risk might be advised to undergo a program of frequent surveillance with mammography. An executable version for IBM-compatible PCs is available from the author upon submission of a PC diskette formatted with MS-DOS.