Joreskog has developed a very general and powerful model and computer program for analyzing relationships among variables, called LISREL. Structural analysis of covariance matrices by Joreskog's LISREL method is proposed as an alternative to regression methodology in the analysis of aptitude-treatment interaction (ATI) data. LISREL resolves some of the basic problems in regression analysis--such as biased estimates caused by unreliability of measures, and interpretative difficulties when there are multiple aptitudes and outcomes. LISREL models range in complexity: from regression models to models involving complex structural relations between latent aptitude and latent outcome variables. (Consideration is also given to the formulation of LISREL models when there are observational units at different levels of aggregation). (Author/JKS)