Since national surveillance for acquired immunodeficiency syndrome (AIDS) began in 1981, the Centers for Disease Control (CDC) has received reports of more than 20,000 cases of AIDS in the United States. As of December 31, 1985, 307 of these cases had been diagnosed in children younger than 13 years of age. The number of cases is increasing rapidly. The number of cases reported in 1985 more than doubled those reported in 1984. The major risk factors in children for acquiring infection with the causative agent, human immunodeficiency virus (HIV), were having a mother known to be infected and/or at increased risk for infection and receiving a transfusion of blood or blood products. Of the 307 children with AIDS, 73% were reported from one of four states: New York, New Jersey, Florida, and California. Most AIDS cases in children occur in black or Hispanic infants and toddlers. The estimated incubation period for AIDS in children has increased each surveillance year, with the longest incubation exceeding 7 years. The prognosis for children with AIDS is poor and infants less than 1 year of age have the shortest survival time following diagnosis. Continued national surveillance for AIDS is mandatory for establishing effective prevention programs to control the spread of the disease. The CDC encourages all health care personnel to report cases of AIDS to their public health departments.