Electric field induced molecular reorientation in stilbazolium salt Langmuir-Blodgett monolayers have been investigated by using rotation-angle second harmonic generation technique. The stilbazolium salt molecules were preferentially oriented along the dipping direction and this anisotropic feature was enhanced by increasing the dipping speed. An external DC electric field (6.7 x 10(5) V/m) forced the molecules to reorient along the field direction, and caused dissociation of aggregate species, as demonstrated by the steady state and time resolved fluorescence measurements.