Bistramide D and K were extracted from a New Caledonian marine colonial ascidian Lissoclinum bistratum and tested against Plasmodium berghei and P. vinckei petteri in mice. Bistramide D was able to reduce parasitaemia by almost 50% in P. berghei infected mice, but the ID50 (>5 mg/kg) was very close to the LD50 (8 mg/kg). In the same assay, bistramide K was less active than bistramide D. The mid-term trophozoite and the old trophozoite were shown to be the stages most sensitive to bistramide D in P. vinckei petteri infected mice. Therefore, bistramides are interesting experimental tools but do not present a major interest as potential antimalarial drugs.