The impact of the world's worst nuclear disaster at Chernobyl in 1986 is reviewed within a framework of a triad of fear, rumour and truth. The scope of the accident, Soviet secrecy about it, and the lack of general awareness of, or disregard for, the effects of radiation created a fertile ground for persistent fears and rumours attributing any health problem to Chernobyl. Scientifically correct answers to health issues have been the means to combat disinformation, and to replace interconnected fears, misconceptions and rumours. To date, according to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2000 Report, based on a review of epidemiological and radiobiological studies, the main radiation-related effect of the Chernobyl accident is an increased risk of childhood thyroid cancer. In addition, the accident has had serious non-radiation-related psychological consequences on the residents of the contaminated territories, resettled populations and clean-up workers. Researchers in search of the truth through epidemiological reasoning are facing serious challenges which are reviewed within this article.