Advances in medical technology and public health are changing the causes and patterns of pediatric mortality. To better inform health care planning for dying children, we sought to determine if an increasing proportion of pediatric deaths were attributable to an underlying complex chronic condition (CCC), what the typical age of CCC-associated deaths was, and whether this age was increasing. Population-based retrospective cohort from 1980 to 1997, compiled from Washington State annual censuses and death certificates of children 0 to 18 years old. For each of 9 categories of CCCs, the counts of death, mortality rates, and ages of death. Nearly one-quarter of the 21 617 child deaths during this period were attributable to a CCC. Death rates for the sudden infant death syndrome (SIDS), CCCs, and all other causes each declined, but less so for CCCs. Among infants who died because of causes other than injury or SIDS, 31% of the remaining deaths were attributable to a CCC in 1980 and 41% by 1997; for deaths in children 1 year of age and older, CCCs were cited in 53% in 1980, versus 58% in 1997. The median age of death for all CCCs was 4 months 9 days, with substantial differences among CCCs. No overall change in the age of death between 1980 to 1997 was found (nonparametric trend test). CCCs account for an increasing proportion of child deaths. The majority of these deaths occur during infancy, but the typical age varies by cause. These findings should help shape the design of support care services offered to children dying with chronic conditions and their families.