This study uses data from the California Linked Homicide File as a basis for evaluating the validity and reliability of homicide data. Case-by-case comparisons of variables reported by both agencies indicate that agreement between law enforcement and vital statistics data is highest with classifying homicides and victim gender and race and lowest with classifying victim age, manslaughters, and police justifiable homicides. The findings from a multilevel analysis examining what types of cases are unable to be linked over the two data-collection systems reveal that homicides involving Hispanic victims, weapons other than handguns, and family members other than intimate partners and homicides involving felonies, other nonfelonies, and negligen...