The ARE was operated successfully in November, 1954, at various power levels up to 2.5 Mw. The maximum steady-state fuel temperature was 1580°F, and there was a differential temperature between the inlet and outlet in the NaF-ZrF4-UF4 fuel of 355°F. The fuel system was in operation for 241 hr before the reactor first became critical and the nuclear operation extended over a period of 221 hr. The final 74 hr of operation were in the megawatt range and resulted in the production of 96-Mwhr of nuclear energy. Effects of various transient conditions on reactor operation were determined.