The present commentary gives a brief overview of the person-oriented and variable-oriented approaches, how they are commonly used in longitudinal research, and what one should take into consideration before using either approach. In addition to presenting an empirical example on girls’ adjustment problems using both approaches, this commentary uses the contributions in the present issue of Merrill Palmer Quarterly to illustrate some of the main issues surrounding these two perspectives. Special attention is also given to the contrast between the person-oriented and variable-oriented approaches in terms of aggregation and disaggregation, model appropriateness and usefulness, and prediction as a goal. Future directions with regard to implementing a personoriented approach are discussed, including the importance of conceptual clarity, practical and theoretical training, and method development.