To examine the potential link between violent video game play and aggressive behavior, reliable and valid measures of the level of violence in video games are required. A range of different approaches have been used in the literature, and it is not clear to what extent they converge or measure different constructs. To address this question, three large longitudinal data sets covering at least 12 months were used from the United States (N= 1,232), Singapore (N= 3,024), and Germany (N= 1,715). Violent content was measured through user ratings, expert ratings, and official agency ratings of individual titles as well as through expert ratings of game genres. The different measures were linked to aggressive behavior both cross-sectionally and longitudinally in all three countries and to the normative acceptance of aggression in Germany and Singapore. User ratings, expert ratings, and official agency ratings were found to be reliable. They showed substantial correlations within each culture as well as between the different cultures, indicating high convergent validity. Measures using nominations of game titles and measures using genre lists showed similar relationships with aggressive behavior and aggressive norms, both concurrently and prospectively over 12 months. Recommendations for a best practice approach to the assessment of violent content in video games are derived from the findings.(PsycInfo Database Record (c) 2020 APA, all rights reserved)