The paper discusses the concept of triangulation in aetiological epidemiology, which involves integrating results from multiple different approaches to strengthen causal inferences. The authors propose a set of criteria for effective triangulation, including comparing at least two approaches with distinct and unrelated sources of bias, addressing the same underlying causal question, considering the duration and timing of exposure, explicitly acknowledging key sources of bias, and ensuring that approaches have expected biases in opposite directions. They emphasize the importance of understanding the expected direction of bias within each approach and comparing results while accounting for differences in exposure duration and timing. The paper provides three illustrative examples to demonstrate how triangulation can be applied in practice, highlighting the potential impact of these factors on the results. The authors conclude by discussing the potential challenges and opportunities of triangulation in aetiological epidemiology, emphasizing the need for further research and methodological development.The paper discusses the concept of triangulation in aetiological epidemiology, which involves integrating results from multiple different approaches to strengthen causal inferences. The authors propose a set of criteria for effective triangulation, including comparing at least two approaches with distinct and unrelated sources of bias, addressing the same underlying causal question, considering the duration and timing of exposure, explicitly acknowledging key sources of bias, and ensuring that approaches have expected biases in opposite directions. They emphasize the importance of understanding the expected direction of bias within each approach and comparing results while accounting for differences in exposure duration and timing. The paper provides three illustrative examples to demonstrate how triangulation can be applied in practice, highlighting the potential impact of these factors on the results. The authors conclude by discussing the potential challenges and opportunities of triangulation in aetiological epidemiology, emphasizing the need for further research and methodological development.