PURPOSE: Although most US women who undergo mammography screening also receive a Clinical Breast Examination (CBE), factors that predict cancer detection during a CBE have not been well studied to date.METHODS: We analyzed 752,081 National Breast and Cervical Cancer Early Detection Program (NBCCEDP) screening records for CBEs performed from July 1, 1995 thru June 30, 1998 on low income women across the US. CBE results are reported as "normal" or "abnormal, suspicious for cancer." Other variables include CBE date, age, race, ethnicity, presence of breast symptoms at screening, and whether the woman had received a prior NBCCEDP-funded CBE. Most (74%) records include mammography dates and results. Tumor stage and size are reported for invasive cancers whether detected by CBE or mammography.RESULTS: Breast cancer was reported on 3,780 records. On 2,224 records, the CBE was suspicious for cancer. On 1,556 records, the CBE was normal. Most (93%) cancer records with a normal CBE had abnormal mammography results. Bivariate comparisons between normal and abnormal CBE records with a cancer diagnosis found significant differences (p <.001) in age, race/ethnicity, presence of breast symptoms, history of a prior NBCCEDP CBE, and tumor stage and size. In a logistic model controlling for these variables, women with breast symptoms were more likely to have their cancer detected during CBE (OR = 7.0, 95% CI = 5.9-8.5), while women with a prior NBCCEDP CBE were less likely to have their cancer detected (OR = 0.7, 95% CI = 0.6-0.8). Compared to women aged 50-59 years, women <40 were more likely to have their cancer detected by CBE (OR = 3.2, 95% CI = 1.9-5.4) but women >/=70 were less likely (OR = 0.7, 95% CI = 0.5-0.9). Larger cancers and those at more advanced stages were much more likely to be detected during CBE.CONCLUSIONS: Among low-income women whose cancers were detected through the NBCCEDP, older women and those who had been screened previously in the program were less likely to have their cancer detected during a CBE, even after controlling for tumor size and stage.