Five children in a family contracted chickenpox during a two-week interval and two died. Clinical observations suggested that both fatalities were due to chickenpox pneumonia and this was confirmed by necropsy study of one patient. In addition, a clinical pattern compatible with varicella pneumonia developed in another sibling who survived. The other two experienced benign illnesses. The children were between the ages of 2 and 10 years. The deaths occurred in a 9-year-old boy and a 6-year-old girl. All children in the family were in good health prior to the varicella-zoster viral infection with the exception of recent intrafamilial rubella. Study of the parents and surviving children failed to reveal an obvious immunologic deficit.