The assessment of early childhood adversity (ACE) is crucial for understanding the impact of aversive events on child development. However, the heterogeneity of assessment tools poses challenges to precision and similarity of measures, and hence interchangeability. In this study, we conducted two separate item-level content analyses of in total 34 questionnaires on early childhood adversity. These include 13 recently recommended questionnaires based on strong psychometric properties. In addition, as a comparison whether these even make it into use, we identified 24 questionnaires through a systematic literature search in an exemplary translationally relevant research field (threat and reward learning). Only, three questionnaires were overlapping across both content analyses, resulting in 34 questionnaires. We identified substantial heterogeneity in the questionnaires and operationalization of ACEs, with limited overlap in ACE exposure types covered by different questionnaires. Specifically, the item-based content analysis of the recommended questionnaires revealed 50 distinct exposure types and a moderate mean overlap (M = 0.28, range: 0.16 - 0.37). For the questionnaires used in the exemplary research field, we identified 40 distinct exposure types and similar mean overlap (M = 0.29, range: 0.19 - 0.36). Furthermore, we observed considerable differences in structural properties across all included questionnaires such as number of items or response formats hampering comparability. We discuss implications on the comparability of results and the interpretation and integration of the existing literature and provide recommendations for future research. In sum, the substantial heterogeneity in the assessment and operationalization of ACE emphasizes their urgent need for methodological solutions to promote comparability, replicability and foster cumulative knowledge generation on this important topic.