Schistosomiasis is endemic in at least 75 tropical and subtropical countries where 600 million people are at risk of which over 200 million are infected. Three species, S. hematobium, S. mansoni and S. japonicum, account for the majority of human infections. There is sufficient evidence that S. hematobium, the predominant etiologic agent for urinary schistosomiasis, is carcinogenic to humans leading to squamous cell carcinoma of the urinary bladder, a relatively uncommon vesical cancer in nonendemic areas. There is limited evidence suggesting that S. japonicum is possibly carcinogenic to humans leading to colorectal cancer and is a risk factor for hepatocellular carcinoma formation. There is inadequate evidence for the carcinogenicity of S. mansoni in humans. S. mansoni may still be linked to hepatocellular carcinoma through potentiating the effects of hepatitis B virus and hepatitis C virus on the liver. In this article, the relationship between schistosomiasis and neoplasia will be reviewed.