OBJECTIVE Regional lymph node involvement is the most important prognostic indicator in patients with solid tumors. Conventional lymph node dissection has not been shown to affect survival and is often associated with considerable morbidity. Intraoperative lymphatic mapping and sentinel lymph node dissection were therefore designed as a minimally invasive alternative to routine elective lymph node dissection in patients with primary cutaneous melanoma. This study examined whether introperative lymphatic mapping and sentinel lymph node dissection were accurate in staging patients with other solid malignancies. METHODS Between 1985 and 1998, 107 patients with breast cancer, 17 with thyroid tumors, 14 with gastrointestinal/gynecologic cancers, six with Merkel cell cancers, and five with squamous cell carcinomas of the head and neck have undergone mapping and sentinel lymph node dissection at the John Wayne Cancer Institute. RESULTS The sentinel node was identified in 96% of patients (98% melanoma). In 36% of patients the sentinel node was the only tumor-positive node (71% melanoma). Eighteen percent of sentinel nodes were negative by hematoxylin and eosin staining but were positive by immunohistochemical staining (15% melanoma). CONCLUSIONS These data suggest that many solid neoplasms have a primary lymphatic channel and lymph node to which it drains. Although sentinel lymph node dissection has been popularized in melanoma therapy, we have found it feasible for treatment of other solid malignancies. This technique may ultimately replace conventional dissection with more accurate staging.