The present invention provides a method of lithographic patterning in order to the strength of the patterned photoresist. The method comprises: applying to a surface to be patterned a photoresist (18) comprising a polymer resin, a photocatalyst generator which generates a catalyst on exposure to actinic radiation, and a quencher; and exposing the photoresist (18) to actinic radiation through a mask pattern (12). This is followed, in either order, by carrying out a post-exposure bake; and developing the photoresist (18) with a developer to remove a portion of the photoresist which has been exposed to the actinic radiation. The polymer resin is substantially insoluble in the developer prior to exposure to actinic radiation and rendered soluble in the developer by the action of the catalyst, and wherein the polymer resin is crosslinked by the action of the quencher during the bake.