The first reliable diagnostic tools for the diagnosis of HIV infection, Western blot and ELISA, were created 20 years ago in the U.S., using initially sera from AIDS patients diagnosed clinically in Switzerland. In Swiss laboratories the diagnosis of HIV infection today is established by using 4th generation screening tests which detect both antibodies and p24 antigen while in the doctor's surgery a rapid antibody assay is used. Confirmation in authorized confirmatory labs relies on a set of different minimal combinations of positive test results derived from both the first and second blood specimen. In patients with a confirmed diagnosis of HIV infection, two further principal questions arise concerning, on the one hand, the virus load and, on the other hand, some clinically relevant properties of the infecting virus (type or subtype, resistance against antiretroviral drugs). The paper starts with a personal flashback to the first days of HIV diagnostics and describes the sensible use of tests available today for answering the above-mentioned principal questions. Alternative methods which can be used when standard tests fail or appear unreliable are mentioned also.