Rabbit lenses were incubated in organ culture with14C acetate for 3, 6, 12 and 20 hours and the nonsaponifiable fraction, composed primarily of sterols, was isolated. The incorporation of acetate into the nonnaponifiable fraction was linear for periods of 3 to 20 hours incubation. The nonsaponifiable fraction was subjected to thin-layer chromatography and 6 bands were observed. On the basis of Rfvalues, one band was tentatively identified as squa-lene, another as lanosterol and a third as a coholesterol-desmosterol mixture. The percentage of the radioactivity incorporated into the eholesterol-desmosterol band increased with incubation time. Conversely the percentage of the radioactivity incorporated into the squalene and lanosterol bands decreased with incubation time, indicating a precursor-product relationship.