Eight invertebrate iridescent viruses (IVs) from diverse host taxa were grown in a common lepidopteran host, Galleria mellonella. The lipid composition of purified virus was assessed by fatty acid methyl esterase (FAME) analysis using a gas-liquid chromatograph. IV fatty acid profiles were markedly different from those of the host tissues. The interrelationships among the IVs did not follow previous serological and genetic findings. We conclude that FAME analysis is not a useful technique for revealing phylogenetic relationships among these viruses.