The dynamics of solvent and rotational relaxation have been investigated in [bmim][BF4]/TX-100/cyclohexane microemulsions with addition of water-using steady state and time-resolved fluorescence spectroscopy as a tool and coumarin 480 (C-480) as a fluorescence probe. The added water decreases the size of the microemulsions; consequently solvent relaxation time increases. The rotational relaxation time of C-480 in microemulsions is almost unchanged with increase in amount of water in microemulsions. (C) 2010 Elsevier B.V. All rights reserved.