1. A new Dicrocoelid trematode, Leipertrema rewelli n.g., n.sp., from the pancreas of an Orang Utan which died in the London Zoological Gardens, is described, and the relationships to other genera are discussed.
2. A male and female Dirofilaria from the peritoneal cavity of the Orang Utan are described and identified as D. immitis (Leidy, 1856).
3. Reasons are advanced for the view that D. pongoi Vogel and Vogelsang, 1980, is a synonym of D. immitis.