Piet Borst started his research lab at the NKI in 1983 and immediately also became director of the NKI. He handed over the directorship to Anton Berns in 1999 but retained his laboratory at the institute until 2015. After closing his lab be remained closely associated with the institute and its research as an honorary staff member. The major focus of his research at the NKI has been on the human parasite Trypanosoma, which is common in Africa and can cause fatal diseases including sleeping sickness. His group has been working on the function and biosynthesis of a previously unknown DNA base, known as base J, found in trypanosomes, and how it can be exploited to treat disease. They have also been investigating the mechanisms of drug resistance in cancer, which is a major problem in the clinic.