The role of occlusal factors in the etiology of temporomandibular disorders (TMD) is currently often estimated to be marginal or non-existent. However, the number of highlevel studies addressing the causal problem of TMD is low and the theoretical basis of the studies is vague. Despite the very large number of published articles discussing evidence-based medicine, the very concept of evidence has remained unclear. The same is true of the concept of causality. The usage of the concepts of evidence and causality appears to be based on mistaken assumptions of their meaning. Therefore, the conclusions drawn from studies on the etiologic role of occlusal factors appear unfounded or premature. Keywords: causality, evidence, occlusion