The association of the polyoxyethylene nonyl phenol (Igepal) in aqueous solution has been studied. The results of the fluorescence quenching of 1-Anthracene sulphonate and Safranine T in nonionic micellar solution of Igepal have been presented. The quenching process was exploited to estimate the aggregation number of surfactant monomer. In the Igepal series the micellar aggregation number systematically varied. From the dynamic light scattering studies in micellar solution the polydispersity of the medium and the diameter of the micelles have been determined. The diameters of the micelles have been increased with increase in the molar mass of surfactants. A reasonable estimation of the surface area of the head group in different micelles has been attempted.