The relationship between the diffusion behavior and the solvent induced crystallization (SINC) was investigated. We have also studied the crystalline structures of PEN crystallized by solvent and compared them with those of thermally crystallized PEN. The diffusion behavior of dioxane at 40 degrees C and 60 degrees C is not pure Fickian but apparent Fickian where diffusion is controlled by crystallization. The diffusion behavior at 25 degrees C is also not pure Case II. The diffusion behavior in DMF is similar to that in dioxane. The samples treated in dioxane above 40 degrees C, which show the Fickian diffusion behavior, exhibit alpha-crystal and spherulitic texture. The sample treated in dioxane at 25 degrees C, which show the Case II diffusion behavior, mainly exhibits beta-crystal and the amoebae structure. The samples treated with DMF mainly show the alpha-crystal, irrespective of treatment temperature. The change of diffusion behavior by varying the treatment temperature affects the crystallization conditions? and crystalline form in SING is changed by the characteristic of solvent.