The laser-induced fluorescence technique is applied to electrosprayed cytochrome c (cyt-c). While no fluorescence was observed for the electrospray of the solution of neutral pH, the fluorescence ascribed to the tryptophane residue was observed for the spray of the acidified solution. The relative intensity of the fluorescence is observed to increase with the distance from the end of the spray needle. This result suggested that the highly charged cyt-e ions which preserve the nonfluorescent compact forms in solution make a conformational change by the loss of solvent in the electrospray and the tryptophane residue becomes more fluorescent.