Some congenital cytomegalovirus (CMV) infections lead to neonatal disease, whereas others have no associated sequelae. To explore a possible role for viral genes as determinants of virulence, portions of the UL144 tumor necrosis factor (TNF)-alpha-like receptor gene, the US28 beta-chemokine receptor gene, and the UL55 envelope glycoprotein B gene from 33 patients with congenital CMV infection were sequenced. Three major UL144 subtypes (A, B, and C) and 2 recombinants (A/C and A/B) were detected. Infection with the least common UL144 subtypes (A, C, A/C, and A/B) was associated with unfavorable disease outcome (P=.04). There was no association between specific subtypes of the US28 and UL55 genes and outcome (P=.864 and P=.765, respectively). Multiple genotypes (implying multiple infections) were detected in tissues from 8 of 10 autopsies. Therefore, polymorphism in the CMV-encoded TNF-alpha-like receptor appears to be associated with congenital CMV disease. Other CMV polymorphisms should be further evaluated for potential relevance to neonatal infection, transplantation, and acquired immunodeficiency syndrome-associated CMV diseases.