Direct-mode scanning electrochemical microscopy with a three-electrode system, which enables the electrochemical potential of the microscope tip to be defined with respect to a reference electrode, has been demonstrated for the first time and used to study fluorescent micropattern formation in fluorescent dye (methylviologen) + ionic conducting polymer film systems. Fluorescence micropatterns were prepared on the film by scanning a platinum or tungsten tip at a potential more negative than - 0.9 or - 1.2 (vs. Ag/AgCl) respectively. The reaction mechanism of the pattern formation was elucidated on the basis of the tip electrode potential and fluorescence characteristics of the films.