A method of achieving frequency doubled lithographic patterning is described. An optical pattern (16) having a first period (p1) is used to expose conventional acid-catalysed photoresist (18) on substrate (20), leaving regions of high exposure (24), regions of low exposure (26) and intermediate regions (22). Processing proceeds leaving regions (24) which received high exposure very polar, i.e. hydrophilic, regions (26) of low exposure very apolar, i.e. hydrophobic, and the intermediate regions having intermediate polarity. A developer of intermediate polarity such as propylene glycol methyl ether acetate is then used to dissolve only the intermediate regions (22) leaving photoresist patterned to have a pitch (p2) half that of the optical period (p1). Alternatively, the photoresist is removed from the apolar and polar regions leaving only the intermediate regions (22) again with the same pitch (p2) half that of the optical period (p1).