Fluorescence emission techniques were applied to the study of aqueous solutions of a hydrophobically modified polyelectrolyte, a block copolymer of sodium poly(styrenesulfonate) (NaPSS) and poly(tertbutylstyrene) (PtBS). At low concentrations, the spectrum of NaPSS/PtBS is essentially identical to that obtained for NaPSS homopolymer. Above a certain concentration, which we identify as corresponding to the critical micelle concentration (cmc); substantial differences are noted in the spectra. Specifically, an increase in the intensity of the excimer peak at 330 nm is observed for the diblock solution relative to the homopolymer solution. The cme is estimated to be in the range of 2 x 10(-7) to 2 x 10(-6) g/g for the diblock.