Wilms' tumour (WT) is an embryonal cancer of childhood and is thought to be derived from embryonic kidney precursor cells. The Knudson two hit model was initially thought to occur in WT, but findings emerging from genetic and cytogenetic studies in the past two decades have implicated several genetic events. Recent techniques in genetic analysis have improved our ability to characterise changes in genes involved in WT which include WT1, CTNNB1, IGF2 and WTX. These genetic events have not only provided insight into the pathobiology of this malignancy, but the recognition of these candidate genes may offer potential targets for novel therapies. In this review, we will provide an overview of the pathological, genetic and cytogenetic characteristics of WT.