Assessing the technique of training by making the trainee a co-therapist, the authors note that similarity in backgrounds and in therapeutic techniques enhances the free exchange of ideas and mutual respect, but may result in mutual blind spots and an overly narrow therapeutic focus. Dissimilar character structures enhance the recognition of countertransferences, while similarity hinders this. When antagonism and distrust dominate over openness, the change of one therapist is indicated. Hindrances to coöperation should be judged on the basis of their closeness to consciousness. It is important that the roles of the co-therapists mesh with the transference needs of the group.