During the mid-1990s, Lange began advocating for the use of combination therapy in the management of HIV/AIDS. He argued that it is an "illusion to think that monotherapy with any antiretroviral agent will have a major and lasting impact on this disease" because the development of drug resistance significantly lowers the efficacy of treatment. In 1996, Lange defended the work of controversial HIV/AIDS researcher David Ho, who treated infected patients by having them swallow 20 pills a day as part of a multidrug "cocktail" regimen. Although this experiment was heavily criticised, Lange explained to "The Wall Street Journal" that "David's work in the past few years has helped to completely transform our understanding of HIV".