After 10 years of screening for breast cancer by mammography in Nijmegen, the predictive value of positive screening results (PV+) was evaluated. The percentage of women with breast cancer in the group of referred women (PV+) for women under age 50 was 16-26%, regardless of the number of screening examinations they had. The percentage of women with breast cancer in the group of women who were biopsied was 25-40%, regardless of the number of examinations. For women aged 50 and over the predictive value was 34-57% and 58-90% respectively. It was further evaluated whether characteristics such as age, Quetelet index, parity, and Wolfe-classification could be used to increase the PV+ in women who were identified as positive by mammography. A logistic regression model analysis showed that true-positive and false-positive cases differ significantly only in terms of age and breast complaints. Although the model had a good fit, it could not be used to distinguish false-positive from true-positive test results.