Extensive scientific investigations often fail to identify specific carcinogens that have caused geographic clusters of cancer cases. In many such examples, public health officials and other experts have concluded that the cluster is not the result of a particular local environmental condition. Despite this conclusion by experts, concerned members of local communities often persist in believing that the cancer cluster was not random. The present study accounts for the persistence of this belief on the basis of two factors: (a) the tendency of the human mind to identify patterns (and causes), rather than randomness; and (b) a lack of social trust in public health experts. It was expected that perceived shared values evoke social trust. Individuals who conclude that public health experts share their values should be more likely to accept the experts’ conclusion that a cancer cluster reflects randomness, not a particular local cause. Individuals who trust authorities should be more inclined than individuals not having trust to accept that a geographic cluster of cancer cases is a coincidence. Data from Swiss students (N= 334) supported these expectations. Additionally, significant gender differences were observed. Females had less trust in authorities and perceived the cancer cluster as less likely to be a result of pure chance than did males. Practical implications of the results are discussed.