Optical proximity effects (OPE) are narrowing the process window in the 0.25micrometers - 0.18micrometers CD range. Hence optical proximity correction (OPC) might be required. These proximity effects and correction strategies are studied in detail in this work. First, an evaluation methodology is derived for the three types of OPE (linewidth differences with pitch, end-of-line effects and corner rounding). Hence, the influence of various parameters on OPE is investigated for negative tone and positive tone resists, since clear differences exist in OPE for dark field and bright field masks. Linewidth differences with pitch are small for negative tone resists, end-of-line effects are less pronounced for positive tone materials. Obviously, optical parameters have an important influence on OPE. Also, loading effects during etch processes deserve attention. Aerial image based proximity correction is evaluated. With respect to CD variations with pitch, important improvements are obtained for some resists, but not for all materials. End-of-line effects and corner rounding are improved by the use of OPC in all our experiments. Superior proximity correction results are expected with the expansion of aerial image based OPC by implementation of resist models.