Objective: To assess the impact of prolonged diagnosis-to-treatment interval (DTI) that falls in the time frame associated with the increasing complexity of planning treatment for patients with locoregionally advanced head and neck cancer (LAHNC). Design: Retrospective study. Setting: The University of Alabama at Birmingham. Patients: An institutional database was searched for all patients with LAHNC who were treated with radiotherapy between 1995 and 2007 at the University of Alabama at Birmingham. After patients with prior treatment for head and neck cancer (including surgery or neoadjuvant chemotherapy), patients younger than 18 years, and patients with stage I or II tumors were excluded, 427 patients remained for analysis. Main Outcome Measures: The DTI was defined as the time in days between the date that a biopsy specimen showing malignancy was obtained and the first day of radiotherapy. Results: The median DTI was 34 days (range, 7-441 days). A longer DTI was not significantly associated with locoregional control (P=.11), distant metastases-free survival (P=.32), or overall survival (P=.07). Conclusion:Aprolonged DTI did not appear to adversely affect outcomes in this cohort of patients with LAHNC. ©2011 American Medical Association. All rights reserved.