HLM by Scientific Software International is a package that does Multilevel Models that are also often called Hierarchical Linear Models (HLMs). An example of a multilevel model is a regression equation showing how studying increases grades. That relationship may differ at different levels, such as teachers within schools within districts.
Learn more about HLM on UTK OIT's Research Software website. Learn when to use it, where to run it, how to learn, and where to get help.