The relationship between very young adolescent mothers and their progeny was studied in terms of fetal development and pup growth. The mothers used in this study had just attained puberty and were still growing; their body weight was about half that of normal full-grown adult females. Still, they were able to conceive and to maintain gestation but growth and skeletal development of their fetuses was significantly retarded. Adolescent dams took in more food during gestation, and about 60% of the intake was used to meet their own growth and development need rather than that of their progeny. During lactation, adolescent dams took in about the same amount of food as did the control, but the pups they were suckling gained significantly less weight than did pups suckled by the control. Retardation of growth and development during gestation, and the continued retardation during lactation, can best be explained by an overall nutritional competition between adolescent dams and their offspring.