OBJECTIVES: To describe varicella complications in healthy and previously ill children hospitalized for varicella and to explore trends in group Aβ-hemolytic streptococcus complications of varicella. METHODS: A retrospective record review of children hospitalized for varicella between January 1, 1990, and March 31, 1994, was conducted in nine large acute care hospitals in Los Angeles County, California. RESULTS: We identified 574 children hospitalized for varicella in study hospitals during the 4.25-year study period (estimated risk of hospitalization, approximately 1 in 550 cases of varicella); 53% of the children were healthy before the onset of varicella and 47% were previously ill with underlying cancers or other chronic illnesses. Children were hospitalized for treatment of complications (n = 427, 74%) or for prophylactic antiviral therapy or observation (n = 147, 26%). Systems involved in complications included skin/soft tissue (45%), neurologic (18%), respiratory (14%), gastrointestinal (10%), and hematologic, renal, or hepatic (8% or less). The mean age of children with skin/soft tissue infections was 2.7 years (range <1 to 16 years) compared with 4.7 years (<1 to 18 years) for other complications. Children with skin/soft tissue and neurologic complications were more often previously healthy ( p <0.05), whereas those with respiratory complications were more often previously ill ( p <0.001). Hospitalizations for skin/soft tissue infections increased during the study period. The proportion of complications as a result of group A β-hemolytic streptococcus infection increased from 4.7% before 1993 to 12.2% for the remainder of the study period ( p = 0.02). CONCLUSIONS: Prior health status was predictive of the type of complications experienced by children with varicella requiring hospitalization. Our data suggest a recent increase in skin/soft tissue complications of varicella requiring hospitalization and an increase in the proportion of complications related to group A β-hemolytic streptococcus. Wide-scale vaccine use should reverse this trend and reduce the overall impact of varicella on both healthy and previously ill children.(J P EDIATR 1996;129:529-36)