The total neutron cross section of Pu240 has been measured at the 1 ev resonance using a crystal spectrometer with good resolution. A detailed analysis was made of the shape of the resonance to obtain the Breit-Wigner level width parameter. The level width was determined to be (32.3 ± 1.5) mv, and the resonance energy was (1.056 ±  0.003) ev.