The halitoxin complex from the marine sponge Amphimedon viridis, collected in the São Sebastião channel (southeastern Brazilian coast), was isolated by gel-filtration chromatography on Sephadex LH-20. Spectroscopic data (1H, 13C and 2D-NMR) of halitoxin from A. viridis indicated that it has the same two alkylpyridine monomers composition of the previously isolated halitoxin from Amphimedon compressa (as Haliclona rubens). Nevertheless, analysis by High Performance Gel Permeation Chromatography indicated that the halitoxin complex of A. viridis has a lower molecular weight (500, 2000 and 5000 Da; the major component corresponding to the fraction of 2000 Da MW) when compared to the previously isolated halitoxin complex from A. compressa. Some pharmacological properties of the halitoxin complex from A. viridis were evaluated in terms of lethality, antimitosis, hemolysis and neurotoxicity. The possible chemotaxonomic value of alkyl pyridine alkaloids is discussed.