Treatment of dual diagnosis patients requires simultaneous treatment of the addictive and the mental disorders. Available data suggest that this does not happen often. In a survey of several psychiatric services, the unit chiefs reported that dual diagnoses were underreported, no plans were present for combined treatment, families were infrequently involved, and few referrals were made for combined treatment. There is a need for competent, experienced clinician teachers who have had positive experience with the treatment of dual disorders. The training of addiction and mental health professionals must include cooperation, understanding, and respect for each other. Cross-training is needed in chemotherapy, psychotherapy, abstinence from alcohol and other addictive drugs, 12-Step programs, spiritual issues, and milieu therapy. Negative attitudes and ignorance must be overcome for this training to take place. Faculty Fellow training programs have provided a beginning in this direction, but have so far involved few professional schools. Some examples of training with regard to referrals, prescribing, and psychotherapy are given. The importance of supervised clinical experience in treating dual diagnosis patients is emphasized. The provision of this experience provides a challenge to specialists in addiction medicine and addiction psychiatry.