Echinococcosis is a near-cosmopolitan zoonosis caused by adult or larval stages of cestodes belonging to the genus Echinococcus (family Taeniidae). The two major species of medical and public health importance are Echinococcus granulosus and Echinococcus multilocularis, which cause cystic echinococcosis and alveolar echinococcosis, respectively. Both are serious and severe diseases, the latter especially so, with high fatality rates and poor prognosis if managed incorrectly. Several reports have shown that both diseases are of increasing public health concern and that both can be regarded as emerging or re-emerging diseases. In this review we discuss aspects of the biology, life cycle, aetiology, distribution, and transmission of the Echinococcus organisms, and the epidemiology, clinical features, treatment, and diagnosis of the diseases they cause. We also discuss the countermeasures available for the control and prevention of these diseases. E granulosus still has a wide geographical distribution, although effective control against cystic echinococcosis has been achieved in some regions. E multilocularis and alveolar echinococcosis are more problematic, since the primary transmission cycle is almost always sylvatic so that efficient and cost-effective methods for control are unavailable.