The purpose of this study was to investigate the relationships among gender, age, and intellectual development. Random samples of 70 females and 70 males were selected with each sex group equally divided into a low-age and a high-age group. The low-age group ranged in age from 16.25 years to 16.75 years and the high-age group from 16.76 years to 17.25 years. The Piaget tasks selected to measure cognitive development were: Conservation of Volume, Separation of Variables, and Equilibrium in the Balance and Combination of Colorless Chemical Liquids. Data from this research produced these findings: (1) males demonstrate a higher level of intellectual development than females, (2) males mature intellectually earlier than females, (3) the value of the conservation of volume task as a component of a battery of formal tasks depends upon whether the decisions are to be made on the basis of the total-task results or on individual task performance, and (4) there appear to be factors other than age and gender that are related to the development of formal operational reasoning. These investigators hypothesize that experiences is another important factor.