The first Jumonji gene was cloned in 1995 by Takeuchi et al. [Takeuchi T, Yamazaki Y, Katoh-Fukui Y, Tsuchiya R, Kondo S, Motoyama J, Higashinakagawa T. Gene trap capture of a novel mouse gene, jumonji, required for neural tube formation. Genes Dev 1995; 9: 1211-22.]. Several genes sharing similar biological features have since been discovered, and are currently grouped into the JMJ family. Interestingly, their deregulation has been associated with cardiac disease, obesity, neurological disorders and cancer. One of the mechanisms underlying their function is gene expression modulation via histone post-translational modifications (PTMs). Increasing evidence of Jumonji deregulation in tumours such as colon, prostate, haematological and breast cancer is continually emerging, hence the need to acquire a better understanding. The Genesapiens.org database of patient arrays allows target expression levels to be investigated in a wide range of cancers, corroborating and extending the role of the JMJ family. Here, we provide an overview of the expression profile and regulation of JMJ family members in cancer, examining the most recent literature in the light of analyses drawn from this database.