Lymphatic mapping in breast cancer patients is a widely used technique for axillary staging, though the optimal technique is not yet established. The purpose of this study was to show that subareolar and subcutaneous injection of blue dye drains to the same sentinel lymph node (SLN) in the axillary basin as does peritumoral injection of technetium (Tc)-labeled albumin. Two injection methods were compared in 154 consecutive patients with newly diagnosed pT1 or pT2 breast cancers (tumor size 5-45 mm). The diagnosis of invasive breast cancer was confirmed by core needle biopsy. Peritumoral injection of 40 to 60 MBq 99Tc-labeled colloidal albumin was performed 18 to 20 hours prior to surgery. In addition, 2 ml of blue dye was injected subcutaneously into the subareolar plexus of the same patients exactly 5 minutes prior to incision and dissection of the SLNs. The blue and hot SLNs were identified by searching for the blue lymphatic vessel and the blue lymph node and by counting the radioactivity with a gamma probe. The correlation between the blue nodes and the hot nodes was examined. Altogether, 154 patients were enrolled in the study. Three patients had bilateral breast cancer, and a total of 157 sentinel lymph node biopsies (SLNBs) were performed. The SLNs could be identified in 155 of the 157 SLNBs (98.7%), and the hot node clearly corresponded to the blue node in 151 of the 155 SLNBs (97.4%). Neither a hot node nor a blue node could be identified in 2 of the 157 SLNBs (1.3%). No concordance between the blue node and the hot node could be achieved in 4 of the 155 SLNBs (2.6%). Injection of blue dye into the subareolar lymphatic plexus shows excellent correlation with peritumoral injection of technetium-labeled albumin concerning the identification of SLNs. Our results support the hypothesis that the lymphatic drainage of the breast parenchyma and the subareolar plexus leads to the same sentinel lymph node. It is a rapid, reliable method for identifying SLNs in breast cancer patients. It is easy to perform, especially in nonpalpable tumors, and it does not disturb surgery by discoloring peritumoral tissue.