Sixteen mothers of 22 infants with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex were followed up for evidence of clinical and immunologic abnormalities. With one exception, all mothers were clinically well at delivery but had evidence of immune dysfunction, with T-cell abnormalities and inverted T4/T8 ratios and/or elevation of serum immunoglobulin levels, particularly of IgG. During a follow-up period that averaged 30 months, AIDS developed in five of the mothers and AIDS-related complex in seven. Twelve subsequent pregnancies in 11 mothers produced four affected infants, suggesting that mothers can be persistently infected. Six mothers were delivered of subsequent infants who remain unaffected. These results suggest that the mothers are the likely source of infection in non—transfusion-associated cases of AIDS or AIDS-related complex in infants, that mothers have persistent immunologic abnormalities, and that they are at increased risk of developing AIDS or AIDS-related complex. (JAMA1985;253:363-366)