A series of N1-acyl derivatives of 5-fluorouracil (5-FU) bearing the residues of palmitic, p-myristoylaminobenzoic, p-oleoylaminobenzoic, and adamantane-1-carboxylic acids have been synthesized. The relative hydrolysis rates for the derivatives under physiological conditions (pH 7.2 and 37 C) have been determined, and it has been shown that the resistance of these compounds to hydrolysis increases as the steric accessibility of the amide group at residue N1of 5-FU decreases. The derivatives easily incorporate into the lipid bilayer; their liposomal preparations show a marked cytostatic activity on human breast lymphoma cells (LD50 ∼1 μM) and are of interest as potential antitumor preparations. In addition, a fluorescent analogue of the above derivatives, 1-[8-(3-perylenyl)octanoyl]-5-fluorouracil, has been synthesized, which is intended for studying the behavior of 5-FU derivatives in cells and tissues by instrumental methods. © 2013 Pleiades Publishing, Ltd.