Seven simple screening tests--hepatitis B profile, urine culture for cytomegalovirus, Mantoux test for tuberculosis, stool examination for ova and parasites, VDRL, complete blood cell count, and vision and hearing screening--were used to evaluate 52 consecutive children at a pediatric clinic for international adoptees. In 63% of these children, unsuspected medical diagnoses were made by a combination of history, physical examination, and appropriate screening tests. When only those children previously examined by a physician in the United States were included in our analysis, the rate of unsuspected diagnosis remained high (67%). Omission of screening tests was the single most frequent cause of missed diagnoses, of which the majority were infectious diseases. More than 50% of our newly established diagnoses carried the potential for long-term sequelae without proper treatment. These data emphasize that internationally adopted children should receive a thorough screening evaluation for medical problems that may adversely affect their growth and development.