The special report summarizes 75 years of scientific contributions to the US Army of the US Army Research Institute for the Behavioral and Social Sciences (ARI). ARI has made lasting contributions to the Army in personnel testing and performance measurement, training and development tools and techniques, leader development and assessment, and organizational effectiveness. While ARI's history centers on personnel testing research, it has grown into a scientific leader across the training, leadership, and organizational science domains as well. ARI's research has substantially improved the Army's capability to recruit, develop, and retain capable and ready soldiers and leaders.