The lipids of two cell types (primary pig kidney and secondary adult pig thyroid) and those of transmissible gastroenteritis virus (TGEV) grown in these cells were studied using 14C-palmitic acid. Differences were demonstrated between the incorporation of isotopically labelled lipid precursors in the two cell types and it was found that the phospholipid and glycolipid profiles of purified TGEV closely resembled those of the host cell in which it was grown.