Sigmund Freud postulated that a person's actions arise from the desire to seek pleasure and avoid pain. Although most defining in one's early years, conflicts coming from this pleasure principle last a lifetime. Freudian psychoanalysis seeks significant childhood events and their attendant fantasies, wishes, and dreams. For Freud, the mind was intimately linked to past experience, both conscious and unconscious. Understanding the mental experiences a person has repressed is therefore key to evaluating present function, along with determining behavioral effects caused by sexual drive (libido) and aggression.

Core of Freudian theory: Factors determining personality develop through oral, anal, and phallic phases in childhood; and through id, ego, and superego during later latency and adolescent periods.

The oral stage of development (birth to about 18 months of age) is marked by libidinal gratification through the lips, mouth, and tongue. Such gratification in the anal phase (about 18 months to age 3) is accomplished through the retention and passing of feces. In the phallic phase, the genitals become primary to libidinal drives. The id (representing the effects of libido and aggression), the ego (standing for self-identity), and the superego (otherwise termed conscience) dominate during the latency period (from the phallic phase to puberty) and adolescence. These forces are shaped by education and socialization with significant others.

Freudian psychoanalysis aims to enable the client to discover unconscious conflicts, with the idea that once they have been revealed, such conflicts respond to rational approaches. In this way, neurotic behaviors may be controlled and abated. During treatment clients are typically asked not to make radical changes in their lifestyles.