A retrospective study was performed on adult patients admitted for surgical drainage of deep neck infections and admitted to the intensive care unit (ICU) during a period of 52 months. Severe infection was defined as septic shock/severe sepsis, mediastinitis, empyema or necrotising fasciitis. Complicated course was defined as ICU stay >8 days, reintubation, tracheostomy, renal replacement therapy, critical illness, myopathy or mortality. Chi-square or Fisher's exact test were used to assess differences and the significance level was controlled for multiple comparisons applying Bonferroni's correction. Fifty-four patients were studied. Variables associated with severe infection (43%) were abscess location (retropharyngeal [52 vs 7%; P<0.001] or multiple [52 vs 13%; P=0.002]), Acute Physiology and Chronic Health Evaluation II>7 (78 vs 13%; P<0.001), Simplified Acute Physiology Score II>29 (73 vs 21%; P<0.001) and first ICU day Sequential Organ Failure Assessment score>2 (77 vs 21%; P<0.001). Variables associated with complicated course (56%) were: parapharyngeal location (60 vs 8%; P<0.001)], Acute Physiology and Chronic Health Evaluation II>7 (67 vs 14%; P=0.001), Simplified Acute Physiology Score II>29 (62 vs 18%; P=0.002) and Sequential Organ Failure Assessment score>2 (68 vs 17%; P<0.001). Serious complications occur frequently in patients with deep neck infections surgically drained and admitted to the ICU. Higher severity scores are associated with both severe infection and a complicated course. Retropharyngeal and parapharyngeal locations are associated with severe infection and a complicated course respectively.