Under experimental conditions legal-sized brook trout, brown trout, and rainbow trout exposed to 110-volt alternating- and 230-volt direct-current electricity suffered an average mortality of 6.4 percent. Immediate mortality amounted to 4.3 percent and the delayed type accounted for 2.1 percent of the deaths. Of the trout exposed to alternating current 11.1 percent died whereas only 2.0 percent of those treated with direct current were killed. There appeared to be no relationship between mortality and either fish size or trout species. Both types of units are considered to be acceptable for stream population studies.