The hydration numbers of some polyhydroxy non-electrolytes and polyoxyethylenated non-ionic surfactants have been determined and found to depend considerably on the method used, the general order being conductometry < ultrasonic interferometry < ir, spectrophotometry. PEG and Tx-100 are exceptions to this trend. The results from ultrasonic interferometry study strongly depend on the data treatment. The maximum hydration obtained using the ir method shows fair agreement with recent nmr and low angle light scattering results on similar compounds. The results indicate the existence of both strongly and loosely bound water molecules with the micelles as well as the penetration of water in the non-polar micellar region. Keywords: hydration, non-electrolytes, non-ionic surfactants, conductometry, ultrasonic, near infrared.