Oftentimes nuclear and hydro are linked together in energy statistics. Of course, they are quite different: nuclear power is generally viewed as dangerous while hydro is viewed as benign. This really is not quite true for either. Despite Three Mile Island and Chernobyl, the safety record for nuclear power speaks for itself: There have been over 13,000 reactor-years of safe commercial plant operation, coupled with an equivalent span of safe operation for nuclear-powered warships. The worst accident by far was Chernobyl, a case of an unsafe reactor design unsafely operated. Hydropower has its opponents, and dam failures are not unknown phenomena. This chapter covers the principal aspects of nuclear and hydropower as energy sources.