The correct approach for solving AIDS causes or pathogenesis questions or any other complicated chronic medical problems is by evaluating all medical evidence concerning each risk group. Namely, a differential diagnosis that considers both infectious and non-infectious causes of diseased should be performed. To test the validity of the HIV-hypothesis, I reviewed the medical literature to evaluate the role of drugs, malnutrition, and infectious agents in the pathogenesis of AIDS worldwide. Detailed descriptions of the studies that I reviewed to evaluate the validity of the HIV-hypothesis were reported. The results indicate that the medical evidence show AIDS is probably caused by the use of illicit drugs, therapeutic use of corticosteroids, and malnutrition. Differential diagnosis indicated that HIV is not involved.