Study of 87 patients (53 adults, 23 males; 34 children, 18 males) with congenital rubella revealed an increased incidence of several HL-A antigens, including HL-A5, HL-A1, HL-A3 and HL-A8, the frequency of HL-A1 being raised because of the statistically significant increase of this antigen in the adult female subjects compared with normal controls. Correlation of the level of seropositivity to rubella virus in 29 normal adult populations, according to racial origin and geographic location, with the frequency of various HL-A antigens revealed the most significant association with HL-A1 (r=0.71). It is suggested that the presence on the cell surface of HL-A1 or the combination of HL-A1 and 8 may favour rubella virus infection.