The study examined the effects of larval trematode infection on the neutral lipid and phospholipid content of Biomphalaria alexandrina infected with Schistosoma mansoni. Uninfected snails were used as matched controls. As determined by qualitative high-performance silica gel thin-layer chromatography (HPTLC), the major neutral lipids present in the whole bodies and digestive gland-gonad complexes in both infected and uninfected snail populations were free sterols, free fatty acids, and triacylglycerols, and the major polar lipids were phosphatidylcho-line and phosphatidyl ethanolamine. Quantitative analysis by HPTLC with visible and UV scanning reflectance densitometry showed the snail's digestive gland lipid level was found to be almost halved in 20 days post infection; a more then 80% reduction being visible after the subsequent 40 and 60 days.