Fluorescence spectra of coal derived asphaltenes sourced from Barari coke plant situated at Dhanbad, India, have been studied as a function of concentration in benzene, toluene and carbon tetrachloride with an eye to study the self-aggregation of the solute. Aggregation has been found to be a gradual process and the concentration characterizing onset of aggregation process coincide for the solvents. The critical aggregation constants (CAC) appear to be ca 90-100 and 180-200 for all the solvents. A small red shift of fluorescence band is observed when traces of water (similar to 0.05%, v/v) are present in carbon tetrachloride solution. (C) 2007 Elsevier Ltd. All rights reserved.