Objective: To define hearing outcomes in children with congenital cytomegalovirus (CMV) infection born to mothers with non-primary CMV infection. Study design: A cohort of 300 children with congenital CMV infection identified by newborn virologic screening at the University of Alabama Hospital and a private community hospital in which the type of maternal infection could be classified constituted the study population. Maternal infections were categorized by analyzing serum samples. Children were followed prospectively and underwent serial audiologic evaluations. Results: The frequency of hearing loss was not different between children born to mothers with non-primary infection (10%) and those with primary infection (11%). Significantly more children in the primary infection group had progressive and severe/profound hearing loss compared with children in the non-primary group. The frequency of bilateral, delayed onset, high-frequency, and fluctuating hearing loss was not different between the 2 groups. The mean age of diagnosis of hearing loss was 39 ± 53 months for children born to mothers with non-primary infection and 13 ± 21 months for the primary infection group (P = .16). Conclusions: Maternal preexisting seroimmunity to CMV does not provide complete protection against hearing loss in infants with congenital CMV infection. © 2006 Elsevier Inc. All rights reserved.