Three flukes, Schistosoma haematobium (urinary blood fluke), Clonorchis sinensis (Chinese liver fluke), and Opisthorchis viverrini (Southeast Asian liver fluke) are, by official decree, Group 1 (fully proven) human carcinogens. Thus, they comprise a group of preventable carcinogens. But considering the situation of prevailing infection, from the lifestyle and food habits of people in the endemic regions, it is unlikely that they are eradicated in the near future. S. haematobium is transmitted by snails and infection is acquired from snail-infested water. C. sinensis and O. viverrini are both transmitted from eating fish. As medically important flukes, it is crucial to understand their biology, and this is an attempt to explain that in the light of the history of their discovery. Further, this is written with a hope that several facts, often erroneously presented in scientific literature, about these flukes are rectified.