A better knowledge of the biochemical and biophysical properties of ce
ll membranes has revealed fundamental concepts concerning the regulati
on of cell functions by intrinsic components of the lipid matrix. Memb
rane lipids exhibit high chemical heterogeneity, with hundreds of dist
inct chemical species; studies of structure-function relationships hav
e unraveled new roles for an increasing number of these lipids as dete
rminants of membrane structure, anchors for membrane-associated protei
ns or signalling agents. Recent observations have confirmed triacylgly
cerol (TG) as a quantitatively minor intrinsic membrane component whic
h seems to play a specific role in important metabolic events such as
cell stimulation or transformation and metastatic processes. The rapid
turnover of the acyl chains into TG of cell membranes suggests an act
ive metabolism. In the plasma membrane, TG appears to be implicated in
the generation of transient non-bilayer domains suspected to be assoc
iated with specific cellular events. This paper summarizes the current
information on TG metabolism and focuses on the potential role of thi
s neutral lipid species on the structure and function of cell membrane
s.