Using liposomes to deliver DNA into different eukaryotic cell types results in higher efficiency and greater reproducibility than other transfection methods. In this unit, Basic Protocol the describes a transient expression system while an Alternate Protocol involves stable transformation and expression of DNA integrated into the genome of the transfected cell. In both protocols, plasmid DNA derived from either crude (miniprep) or purified (through CsCl) preparations is mixed with a liposome suspension comprised of cationic lipids and applied to monolayer cell cultures.