Clinical trials have demonstrated that fast neutron radiotherapy is the treatment of choice for advanced inoperable salivary gland tumors. A three-field technique utilizing a medically dedicated cyclotron to produce fast neutrons is described for the treatment of adenoid cystic carcinoma of the parotid. This three-field technique utilizes the cyclotron's multi-leaf collimator system to treat large asymmetric fields, which spare normal tissues otherwise treated with conventional wedged pair techniques. Field geometry, field weightings, and beam normalization will be discussed in relation to this three-dimensional treatment volume.