Mother-to-child transmission (MTCT) is the most common source of HIV infection in children. One topic that has received virtually no attention in MTCT-related research and programming is the psychosocial consequences among parents and families of receiving a definitive diagnosis of infant HIV status. This study explored experiences of HIV-infected mothers in Johannesburg, South Africa, regarding infant testing and diagnosis. Data collection entailed a key informant workshop and repeat interviews with a convenience sample of 31 HIV-infected mothers. While early testing was desirable, diagnosis had both beneficial and detrimental psychosocial effects, especially in instances of serodiscordance. Programmatic implications are discussed.