<jats:p>Further investigations of the bryozoan Amathia wilsoni have yielded amathamides C-F, four new bromine-containing alkaloids, which are closely related in structure to the previously described amathamides A and B. There is no significant variation in the alkaloid content of different colonies of the bryozoan at the same location, but differences occur between samples of the bryozoan which have been obtained from different collection sites.