Liposomes, which are self-closed vesicular structures composed of(phos
pho)lipid bilayers, have attracted considerable interest since their d
iscovery in the 60's. Because of their organization and the versatilit
y of their physicochemical properties these vesicles have been extensi
vely studied as models for biological membranes. Since liposomes can s
equester bioactive molecules, they are also widely used as drug delive
ry systems. The present report focuses on the renewed interest in the
field with the advent of ''sterically stabilized'' (Stealth(R)) liposo
mes which, compared to ''conventional'' liposomes, have much longer ci
rculation times in vivo, and on the use of cationic liposomes in non-v
iral gene delivery strategies. Liposomes are also very promising antig
en carriers that can be used to design peptide-based synthetic vaccine
s.