In southern Italy diagnostic delay in breast cancer patients has been demonstrated to be related to the level of education and residency in rural areas. In order to verify whether late breast cancer diagnosis was actually in decline as a result of improving socioeconomic conditions and ongoing prevention programs, we evaluated clinical data from the tumor registry of the National Cancer Institute, Naples. Four thousand two hundred forty consecutive breast cancer patients admitted to our institution from 1986 to 1997 were grouped into four 3-year periods according to their admission date. Using multiple logistic regression, chi(2) for trend and beta-coefficient were calculated in each pT and pN categories in order to discover the trend for the 1986-1997 period. A progressive, statistically significant decrease in the number of patients with advanced cancer at the time of diagnosis was observed over the study period. In particular, chi(2) values for trend for each pT category, over the study period, were pT1 119.4 (P < 0.001) with positive chi-coefficient, pT2 13.4 (P = 0.003) with negative beta, and pT3-pT4 152.2 (P < 0.001) with the strongest negative beta. Changing patterns of breast cancer stage at diagnosis have been demonstrated in women living in Southern Italy. They are consistent with an increasing orientation toward prevention. Data from hospital tumor registries are a useful source of information on diagnostic delay. Copyright 2000 American Health Foundation and Academic Press.