Recently there have been several news items about possible cancer clusters in the Australian media. The term "cancer cluster" is used when an unusually large number of people in one geographic area, often a workplace, are diagnosed with cancer in a short space of time. In this paper the authors explore this important health issue using probability theory and in particular the binomial distribution. This paper also illustrates how students can use the binomial distribution to gain a more thoughtful approach to cancer clusters and demonstrates how mathematics should be applied in practice.