We compared breast cancer mortality rates in the period 1985-2000 in two areas of the province of Florence, Italy, where breast cancer screening programmes started in the 1970s (early screening (ES) area) and in 1990s (late screening (LS) area). The overall age-standardised mortality decreased in the whole period by 40.9% in the ES area (P<0.001), and by 11.3% in the LS area (P=0.030). Significant decreases in the ES area were detected in groups aged 45-54 years (61.1%; P= 0.018) and 65-74 years (44.7%; P= 0.049), whereas in the LS area no significant decrease was detected in any age group. The relatively low compliance in the first years of the programme in both areas, and the long enrollment period in the LS area could have reduced the effect on mortality. Our findings suggest that the drop in mortality in the ES area (41%) could be explained by both service screening and better care. The slight decrease in mortality in the LS area (11%) could be mainly due to better care. A reduction of about 30% is attributable to screening in the ES area over the period 1985-2000.