Three research studies were designed to test the explanatory powers of two broad psychoanalytic hypotheses about the nature of unconscious mental functionings. Both hypotheses bear directly on the psychoanalytic theory of therapy. The first, the Dynamic hypothesis, assumes that unconscious mental life is determined by the dynamic interactions of unconscious forces that take place in accordance with the pleasure principle beyond the patient's control. The second, the Unconscious Control hypothesis, while not excluding unconscious dynamic interactions, assumes that the patient unconsciously may use his higher mental functions and that he exerts a certain degree of control over his unconscious mental life. He uses this control to develop goals, to test the therapist (and at the same time his pathogenic beliefs), and to regulate the coming forth of repressed mental contents, bringing them forth when he unconsciously decides that he could safely experience them. The studies demonstrate that quantitative, reliable research methods can be used to test basic psychoanalytic hypotheses about the nature of unconscious mental functioning. The findings are compatible with the Unconscious Control hypothesis as described above.