Recent reports suggest that early onset, severe unilateral sensorineural hearing loss (USNHL) in children may be associated with significant deficits in auditory and psycholinguistic skills and school performance. This report reviews a consecutive series of 324 children and adolescents (202 males, 122 females) with documented USNHL evaluated at the Boys Town National Research Hospital. The left ear was affected in 168 (52%) and the right ear in 156 (48%). Based on speech frequency threshold averages (i.e., 500, 1000, and 2000 Hz), the losses were classified by severity as follows: borderline, 43 (13%); mild, 51 (16%); moderate, 40 (12%); severe, 19 (6%); profound, 31 (10%), and anacusic, 50 (15%). The remaining 90 children (28%) had high frequency losses (i.e., above 2000 Hz). The mean and median age of diagnosis were 8.78 years and 7.75 years. Temporal bone imaging studies, auditory brainstem responses (ABRs), and vestibular evaluations were performed on selected cases. Etiology was uncertain in 34.8% of cases, while hereditary factors (12.6%), head trauma (10.8%), and perinatal risk factors (10.7%) were the most commonly identified etiologies. Thirty-one percent of the children had scholastic or behavioral problems in school. A concerted effort aimed at early identification and intervention in cases of USNHL is warranted.