Acute GVHD (aGVHD) is an immunologic complication of allogeneic hematopoietic cell transplantation (HCT) that can range from mild to life-threatening. Models to predict patients at risk of poor outcomes have been developed using both clinical and laboratory data, and the time to test these models in clinical trials has arrived. However, each modeling method has its potential advantages and limitations. In this mini-review, we summarize recent refinements to these models. We also suggest avenues for improving risk stratification through further studies of a patient's healing capacity and predisposition to endothelial damage, two factors that impact aGVHD outcomes but are absent from the current risk stratification models.