Our first objective was to assess changes in non-attendance, proportion of advanced breast cancer and survival in Malmö Mammographic Service Screening Program, MMSSP, compared to a former trial, Malmö Mammographic Screening Trial, MMST. Our second objective was to describe non-attenders in MMSSP in socio-economic terms and risk for advanced breast cancer compared to attenders. Information from hospital and national registers was used to identify 33,800 women invited to service screening in MMSSP 1990-93. Attendance rates at first screening, the proportion of advanced breast cancers (Stage II-IV) and survival among non-attenders in MMSSP were compared to the non-attenders and with the control group of the former trial, MMST. Various socio-economic factors were assessed as potential predictors of non-attendance in MMSSP. Odds ratios (OR) and 95% confidence interval (CI) were computed. Incidence of breast cancer during a 10-year-period, relative risks and 95% CI among non-attenders compared to attenders in MMSSP were computed. Attendance rates were significantly lower in MMSSP but a lower proportion of advanced breast cancers and a somewhat better survival among breast cancer cases (not significant) was seen in non-attenders in MMSSP compared to MMST. In MMSSP non-attendance was associated with being unmarried, being born abroad, being not currently employed, crowded housing conditions and low income. Incidence of advanced breast cancer was significantly higher among non-attenders than among attenders. Attendance has decreased over time and potential reasons are discussed. Stage distribution and survival among non-attenders seem to have improved. Several socio-economic factors predict non-attendance and non-attenders are at higher risk for advanced breast cancer.