The Joreskog and Sorbom LISREL (linear structural relations) method is investigated as an alternative to regression analysis in studies of aptitude-treatment interactions (ATI), to solve problems caused by unreliability of measurements and by large sets of variables. A study reported by M.J. Behr is reanalyzed. This study investigated relations between verbal and figural aptitude variables and outcome variables within one verbal and one figural treatment, teaching modulus seven arithmetic to prospective elementary teachers. The relations between latent aptitude variables and latent outcome variables are studied in four LISREL models with either one or two latent aptitude variables (interpretable as a general factor and verbal and figural ability, respectively), and with two sets of latent outcome variables (interpretable as learning/retention and computation speed/understanding). No significant interaction is found, but tendencies towards interaction are noted. It is concluded that LISREL has several advantages in the analysis of ATI studies, but also that the power of the test of ATI effects is low, particularly when there is a high correlation between the latent aptitude variables. (Author/GDC)