During 1970–1984 AIDS-era research converged on establishing a retroviral etiology through serology, epidemiology, and early virology. Researchers developed serologic assays to detect antibodies against Human T-lymphotropic virus type III and mapped seroprevalence across AIDS patients and at-risk groups, enabling population screening and diagnostics, while immunopathology work revealed immune disruption at cellular and systemic levels. Direct virology provided proof of a retrovirus infection through proviral DNA presence, isolation, and continuous culture of cytopathic agents, and antigenic mapping refined the tools for immune recognition and diagnostic development. Historical Significance: Key breakthroughs unified virology, immunology, and clinical observation, showing that the AIDS retrovirus uses the CD4 receptor as a cell entry point and establishing a foundational paradigm for entry biology and targeted intervention. The first isolation and sustained culture of the AIDS virus, together with serologic detection of antibodies in patients and at-risk populations, anchored diagnostics, surveillance, and vaccine research trajectories. Monoclonal antibody analyses elucidated mechanisms of virus-induced immunodeficiency and informed antigenic characterization across related retroviruses, shaping subsequent research into immune dysfunction and therapeutic strategies.