Neutrino flavor oscillations are discussed in terms of an explicit model. T
his model consists of two coupled Dirac equations with three parameters: th
e electron neutrino mass, the muon neutrino mass, and a coefficient which d
escribes the possibility that the neutrino can flip flavor. The system is d
iagonalized to obtain the exact eigenvalues and eigenfunctions. The system
is then quantized and the neutrino flavor wave functions are derived direct
ly from the quantized fields. It is shown that neutrino flavor oscillation
probabilities are recovered in a quantum field theory treatment only in the
ultrarelativistic limit. (C) 1999 American Association of Physics Teachers
.