Poly(ethlene terephthalate)(PET) film was treated with organic solvent in order to improve the dyeing properties. The effect of organic soment pretreatment on dyeing proerties of PET film has been explained in terms of dyeing transiltion temperature and degree of swelling. The results of the investigation are as follows. (1) The degree of swelling of PET film with organic solvent pretreatments are decreased in the order of benzyl alcohol>monochlorobenzene>perchloroethylene>toluene>n-butanol. (2) The dyeing transition temperatures (TD) of PET film are lowered by organic solvent pretreatments and the degree of lowering is proportional to degrees of swelling. (3) The increased dye uptake of PET film, from which solvents were removed after swelling, is in linear relationship with degrees of swelling or solvent contents(mole/kg). (4) The PET films containing solvent have more dye uptake than films, from which solvent removed, due to carrier action of solvent contained and benzylalcohol and monochlorobebzene are especially effective. (5) The more dye uptake in C.I. Disperse Orange 3 than C.I. Disperse Violet I Was recognized for all solvent being used.