In this paper the influence of several factors on the rheological behaviour of aqueous systems containing 0.25 and 0.50 mol(L of a polyoxyethylene fatty alcohol has been analysed. Such factors are: temperature, pH, kind of alkali used to increase the pH and HLB of the surfactant. The influence on the rheological parameters when samples are introduced into the sensor systems either as liquids or as liquid crystals has also been studied.