Background: Despite IMRT technological advances, toxicity in LAHNC pts remains extreme. Different IMRT techniques have been developed, including sequential boost (SeqB) and simultaneous integrated boost (SIB). However, the relative efficacy and toxicities of each technique remain unexplored. Methods: 209 pts with LAHNC were treated with SeqB (n = 68) or SIB (n = 141). A matched cohort multi-institution analysis was used. All 209 pts received 69.3Gy in 33 fxs of 2.1Gy to gross disease. SiB pts received 1.6Gy daily in 33 fxs (52.8Gy) to prophylactic nodes; SeqB pts received 2.1Gy for 24 fxs (50.4Gy) to gross disease and prophylactic nodes, followed by a boost of 18.9Gy in 9 fxs to gross disease. All pts received concurrent chemotherapy, 95% with weekly paclitaxel (40mg/m2) and carboplatin (AUC 1). Targets and organs at risk (OARs) contours, dose constraints, dosimetric plan evaluation, and toxicity assessment were alike and performed by a single experienced physician. Weekly toxicities were graded using the CTCAE. Tumor control and survival were estimated via Kaplan-Meier. Results: Median FU was 30.6 mo. At 3 years, OS was 69% for SeqB and 79% for SIB cohort (p = 0.13). 3-yr DFS was not different (63% vs. 73%; p = 0.27). There were no significant differences in local, regional, or distant RFS. There were no differences in weight loss (p = 0.291), incidence of G-tube (p = 0.494), or in prolonged G-tube dependence (p = 0.465). Rates of grade 3 or 4 dysphagia were higher for SiB than for SeqB (81% vs. 55%, < 0.001) as well as dermatitis (78% vs. 58%, p = 0.012). Fewer SIB pts received the total 69.3Gy IMRT dose due to acute toxicity (93% vs 100%; p = 0.03). OARs mean dose, Dmax, and percent volume receiving 30Gy and 70Gy were not statistically different between the two cohorts. Conclusions: There were no significant differences in tumor control or survival outcomes between the two IMRT delivery approaches. The SeqB IMRT technique resulted in lower grade 3 and 4 acute radiation dermatitis and dysphagia compared to SiB, and more pts completed treatment with SeqB than did pts treated with SiB IMRT. SeqB should be considered for LAHNC to lower treatment toxicity and improve delivery.