The active encapsulation of doxorubicin (DOX) into fluorinated liposomes, the stability of these liposomes with respect to encapsulated DOX release in buffer and in human serum, and their H+/Na+ membrane permeability have been investigated and compared to those of their conventional hydrogenated analogues. These fluorinated liposomes are made from highly fluorinated phosphatidylcholines and contain a fluorinated core within their membrane. We found that the presence of this fluorinated core is not a barrier for the active encapsulation of DOX. Efficient (> 90%) and stable loading could be achieved using a transmembrane ammonium sulfate or even, in the absence of Na+, a transmembrane pH gradient. The higher H+/Na+ permeability found for the fluorinated membranes, as compared to conventional ones, is responsible for the lower stability observed for the DOX-loaded fluorinated liposomes when incubated in a physiological buffer (PBS) or in human serum. It is also noticeable that the retention of DOX is increased in human serum and for the liposomes whose membranes are in a gel or in a semi-fluid semi-gel state at 37 degrees C.