The objective of this exploratory study is to characterize by means of drawings if the developmental patterns in the graphic representation of organ and organ systems progresses related to age of participants. Secondly, whether there is an integration of sex organs into the internal body image. The drawings representing the inside of the body in the conception of 396 Brazilian children of both sexes aged 5 to 11 year-olds and 237 adolescents boys and girls of ages 12 to 14 year-olds were classified according to a guide for qualitative scoring criteria. The relationship between age and drawings was found consistent with developmental patterns. The integration of sex organs into the drawings representing body images, were equally evident with pre-adolescents of both sexes and are discussed both on the perspective of psychoanalytical theory and mental models. (Contains 4 tables and 10 figures.)