HDPE or isotactic PP film, (a) nonfilled and (b) filled (CaCO3, SiO2, MgO, CaO, TiO2 and Ca stearate), was exposed to corona discharge in the presence of air at 23 degrees C. As the unit energy was raised, the deg. of oxidn. in the topmost a- and b-layer rose. At <3 kJ/m(2), the a-layer was 4 x as apt to oxidize as the b-layer; at =3 kJ/m(2), both film types were nearly equally oxidized and N occurred in either type (from air). Over 0-24 kJ/m(2) the deg. of oxidn. rose (a) 56 and (b) 2.5 times. The surface b-layers contained much less filters than the bulk content. To make printing ink adhere in 70% required the films to be activated with (a) 0.75 and (b) 1.5 kJ/m(2).