Structural equation models (SEMs) are multivariate specifications capable of conveying causal relationships among traits. Although these models offer insights into how phenotypic traits relate to each other, it is unclear whether and how they can improve multiple-trait selection. Here, we explored concepts involved in SEMs, seeking for benefits that could be brought to breeding programs, relative to the standard multitrait model (MTM) commonly used. Genetic effects pertaining to SEMs and MTMs have distinct meanings. In SEMs, they represent genetic effects acting directly on each trait, without mediation by other traits in the model; in MTMs they express overall genetic effects on each trait, equivalent to lumping together direct and indirect genetic effects discriminated by SEMs. However, in breeding programs the goal is selecting candidates that produce offspring with best phenotypes, regardless of how traits are causally associated, so overall additive genetic effects are the matter. Thus, no information is lost in standard settings by using MTM-based predictions, even if traits are indeed causally associated. Nonetheless, causal information allows predicting effects of external interventions. One may be interested in predictions for scenarios where interventions are performed, e.g., artificially defining the value of a trait, blocking causal associations, or modifying their magnitudes. We demonstrate that with information provided by SEMs, predictions for these scenarios are possible from data recorded under no interventions. Contrariwise, MTMs do not provide information for such predictions. As livestock and crop production involves interventions such as management practices, SEMs may be advantageous in many settings.S TRUCTURAL equation models (SEMs) (Wright 1921;Haavelmo 1943) are multivariate models that account for causal associations between variables. They were adapted to the quantitative genetics mixed-effects models settings by Gianola and Sorensen (2004). These models can be viewed as extensions of the standard multiple-trait models (MTMs) (Henderson and Quaas 1976) that are capable of expressing functional networks among traits. Gianola and Sorensen also investigated statistical consequences of causal associations between two traits when they are studied in terms of MTM parameters, expressed as functions of SEM parameters. Additionally, these authors developed inference techniques by providing likelihood functions and posterior distributions for Bayesian analysis and addressed identifiability issues inherent to structural equation modeling.The work of Gianola and Sorensen (2004) was followed by several applications of SEMs to different species and traits, such as dairy goats (de los Campos et al.