Fusaproliferin (FP) is a sesterterpene mycotoxin produced by some species of Fusarium, common contaminants of maize. Toxicity assays on Artemia salina L. brine shrimp larvae using FP and its derivatives showed that toxic activity of the metabolite increased after acetylation of the two hydroxyl groups and was reduced when the naturally occurring acetyl group was removed. In chick embryotoxicity bioassays, severe teratogenic effects were observed in 20% of the embryos exposed at 5 mM FP on day 1. In particular FP was responsible for cephalic dicotomy, macrocephaly, and limb asymmetry. At the same concentration, FP also caused pathological changes such as hemorrhaging on the surface of the wings, skull, and legs. Incomplete closure of the umbilicus was seen in 30% of embryos inoculated with 5 mM of FP on day 1 and in 20% of those inoculated on day 11. Keywords: Fusaproliferin; Fusarium proliferatum; chick; embryotoxicity; teratogenic; mycotoxin