A retrospective review of the records of 501 previously untreated patients from January 1, 1965 through December 31, 1986 with squamous cell carcinoma of the oral cavity was undertaken to ascertain the prevalence of ipsilateral neck node metastases (NM) by neck level. The 501 patients underwent 516 radical neck dissections. Patients were grouped by clinical neck status at the time of neck dissection: elective dissection (ED) in the N0 neck, immediate therapeutic dissection (ITD) in the N+ neck, and subsequent therapeutic dissection (STD) in the neck observed which converted clinically to N+. Pathologically identified NM occurred 34% of the time in ED, 69% in ITD and 90% in STD. The sensitivity, specificity, and overall accuracy of the clinical exam was 70%, 65%, and 68%, respectively. Detailed analysis was performed for each group based on the primary site. This revealed a prevalence of NM in level IV of 3% (five of 167) for ED versus 17% (49/296) for ITD + STD (P less than 0.001). Tongue, retromolar trigone, and cheek did not have NM in level V in any group. The prevalence of NM in level V for floor of mouth or gum primaries was less than 1% (one of 109) in ED versus 6% (ten of 167) in ITD + STD (P less than 0.03). These data support the trend toward selective limited neck dissection in both N0 and N+ patients. Further, they provide the foundation for planning of future prospective trials to assess the efficacy of modifications in the extent of neck dissection.