The fluorescence spectra and decay curves of a series of poly(ethylene glycols), EOx-Py-EO87-Py-EOx, were obtained in dilute solution. These pyrene-labeled polymers have a central chain of 87 (number average) monomer units separating the two pendant pyrene groups and two flanking end chains of equal length, x, where x = 2, 12, 17, or 47 (number average) monomer units. In toluene, tetrahydrofuran, and benzene, small decreases in the cyclization rates of these polymers were observed with increasing length of the end chains. The rate of ring opening in the chain interior was found to be twice as fast as ring opening at the chain ends. These results are consistent with theoretical predictions of interior cyclization and the effects of excluded volume, respectively. Rates of end-to-end cyclization were found to be slower than expected by comparison to the rates of interior cyclization. Also, dilute solutions of interior-labeled polymer show small amounts of pyrene dimers which are preassociated intramolecularly. These results are believed to arise from differences in the local concentration of pyrene in interior- and end-labeled polymers. In water, there is evidence of hydrophobic association of the pyrene groups, and the extent of preassociation decreases with increasing chain length.