All slides from 607 consecutive invasive breast carcinomas from 583 patients were reviewed. Margin distance, composite width of invasive carcinoma, and number of ducts with intraductal carcinoma within the one-half low-power field (LPF) adjacent to the final margin were recorded. Final margin groups were positive (carcinoma at margin), near (< or = 1/2 LPF of margin), and negative (> 1/2 LPF). There were 39 ipsilateral breast failures (IBFs), and 63 patients (10.8%) developed distant metastases (DMs). Decreasing margin distance and increasing amounts of carcinoma near the margin were associated with IBF and DM. The 5-tiered composite factor of margin distance and amount of carcinoma near margin (negative margins, near least amount, near intermediate amount, near greatest amount, and positive margins) resulted in 12-year IBF rates of 9%, 6%, 18%, 24%, and 30%, respectively (P < .001). The composite factor, margin amount of carcinoma near margin, and invasive carcinoma/initial excision specimen dimension ratio were the most precise parameters assessing excision adequacy and, ultimately, IBF risk. The amount of carcinoma near the margin and volume of excised parenchyma related directly to the amount of residual carcinoma in the adjacent breast parenchyma.