Prenatal diagnosis of maternal diseases common to HIV infection may alert the clinician to potential HIV infection in the infant, with resultant early diagnosis and treatment. Although of limited value in the first months of life, imaging studies can be beneficial in selected cases and may be the first clue to the diagnosis of AIDS. The multisystem involvement frequently seen in AIDS necessitates multiple imaging modalities. Recurrent pneumonia, particularly Pneumocystis carinii pneumonia, may be first suggested by the chest radiograph. Brain atrophy and white matter disease, shown on MR imaging or CT early in life, can suggest AIDS. Ultrasonography is not only crucial for prenatal fetal assessment, but it also is important for evaluation of the common findings of hepatomegaly, adenopathy, and tumors, as well as inflammatory fluid collections.