For the first time, in "The Infantile Genital Organisation" (1923), Freud defines the phallic stage (3-5 years of age) that succeeds the oral and anal stages, which are pregenital organizations.

It corresponds to the unification of the component instincts under the primacy of the genital organs, from infancy onwards, being an organization of sexuality very close to that of the adult (genital stage).

In Three Essays on the Theory of Sexuality (1905), Freud compares the phallic and genital stages: This phase, which already deserves to be described as genital, presents a sexual object and some degree of convergence of the sexual impulses upon that object; but it is differentiated from the final organisation of sexual maturity in one essential respect. For it knows only one kind of genital: the male one... According to Abraham (1924), it has a biological prototype in the embryo's undifferentiated genital disposition, which is the same for both sexes" [SE, VII, 199 (note added 1924)]

Thus Freud postulates that boys and girls at the phallic phase are concerned with the polarities of phallic and castrated and he believes that children have no knowledge of the vagina at this stage.

The discovery of the anatomical distinction between the sexes (presence or absence of the penis) gives rise to penis envy in girls and castration anxiety in boys because the castration complex is centered on the phantasy that the girl's penis has been cut off.

The girl's leading erotogenic zone is located at the clitoris, which from Freud's viewpoint is homologous to the glans penis.

Klein, Horney and Jones consider that the girl has a primary intuitive knowledge of the vaginal cavity and the conflicts of the phallic fase have merely a defensive function against her anxieties related to femininity.

During the phallic stage, the culmination of the Oedipus Complex (which connotes the child's situation in the triangular relationship), follows different paths for both sexes in the process of its dissolution: threat of castration (boys) and the desire for a baby as a symbolic equivalent to the penis (girls).