A phytochemical investigation of the 80% ethanolic extract of stem bark of Vismia orientalis Engl. (Guttiferae or Clusiaceae), a plant used in traditional medicine in Tanzania, resulted in the isolation and spectroscopic characterisation of 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone, emodin, vismione D and bianthrone A1. Vismione D exhibited a broad range of antiprotozoal activities against Trypanosoma brucei rhodesiense and T. cruzi (IC50 < 10 micrograms/mL), Leishmania donovani (IC50 0.37 micrograms/mL) and Plasmodium falciparum strain K1 (IC50 1.0 microgram/mL). However, it was also slightly cytotoxic against human L6 cells (IC50 4.1 micrograms/mL). Emodin showed antileishmanial activity (IC50 2.0 micrograms/mL), while its IC50 against L6 cells was 20.3 micrograms/mL. Other antiprotozoal activities observed for emodin against both Trypanosoma species and P. falciparum, for bianthrone A1 against T. b. rhodesiense and P. falciparum, and for 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone against T. b. rhodesiense, L. donovani and P. falciparum were in the range of 10 to 50 micrograms/mL. None of the compounds showed antibacterial or antiviral (including also HIV) activity.