GUSAR is cheminformatics software that creates quantitative structure-activity relationship (QSAR) models to predict biological activity from chemical structures. It can build models from large datasets using 2D molecular descriptors and unique algorithms. GUSAR also provides pre-built QSAR models for acute rat toxicity and affinity to antitarget proteins. The software runs locally and can rapidly handle large datasets, creating robust and predictive QSAR models for biological activity prediction.