We have observed cyclotron resonance in the three dimensional organic
conductor d(2)[1,1;0]-(DMe-DCNQI)(2)Cu. An effective mass of (3.35+/-0
.2)m(e) is obtained, in excellent agreement with the effective mass de
duced from de Haas-van Alphen measurements. This result rules out the
possibility that electron-electron interactions play an important role
in these materials.