A probabilistic causal chain A→B→C may intuitively appear to be transitive: If A probabilistically causes B, and B probabilistically causes C, A probabilistically causes C. However, probabilistic causal relations can only guaranteed to be transitive if the so-called Markov condition holds. In two experiments, we examined how people make probabilistic judgments about indirect relationships A→C in causal chains A→B→C that violate the Markov condition. We hypothesized that participants would make transitive inferences in accordance with the Markov condition although they were presented with counterevidence showing intransitive data. For instance, participants were successively presented with data entailing positive dependencies A→B and B→C. At the same time, the data entailed that A and C were statistically independent. The results of two experiments show that transitive reasoning via a mediating event B influenced and distorted the induction of the indirect relation between A and C. Participants' judgments were affected by an interaction of transitive, causalmodel-based inferences and the observed data. Our findings support the idea that people tend to chain individual causal relations into mental causal chains that obey the Markov condition and thus allow for transitive reasoning, even if the observed data entail that such inferences are not warranted. Transitive reasoning enables judgments about unobserved relationships based on indirect evidence. If one observes that object A is heavier than object B, and that B is heavier than C, one can infer that A is heavier than C. Not all relations, however, are transitive. If A is the mother of B, and B is the mother of C, this does not mean that A is the mother of C.We investigate whether and to what extent people reason transitively about causal relations, even when the conditions for transitive inferences do not hold true. We focus on probabilistic causal chains of the type A→B→C, where individual relations A→B and B→C can be combined to form a chain A→B→C to make probabilistic inferences from the chain's initial event A to the terminal event C. First, we specify the conditions under which transitive reasoning in causal chains is valid. We then report the findings of two experiments investigating whether people make transitive inferences even when the available data entail that such inferences are not warranted.Our research builds on the idea that people represent the world in terms of mental causal models (