This lecture is about vector-borne diseases in the 21st century. I approach it first from a historical perspective. To understand what is going to happen in the next century we need to understand what people like us have done in the past. Next, four case studies illustrate some of the changing ecology and the changing epidemiology of these diseases. These include the plague epidemic in India, dengue hemorrhagic fever, West Nile virus and yellow fever, which truly hasn't emerged yet, but has great potential to do so. Finally, some of the factors responsible for this dramatic global resurgence in the past twenty years and approach to these problems are discussed.