Viscoelastic properties during thermo-induced gelation of a binary poloxamer (Pluronic F68)/water system have been determined by oscillatory shear and shear stress relaxation measurements. The polymer concentration has been kept constant at 35 wt %. A sol-gel transition is observed in the range 34-37 degrees C. The oscillatory shear data at temperatures around the gel temperature reveal a complex pattern of behavior. The results cannot be described by a single Maxwell element behavior as demonstrated by converting the data to Cole-Cole plots. Shear stress relaxation experiments show that the stress relaxation at the lowest temperatures of measurement (34 and 35 degrees C) can be described initially by a single exponential followed at longer times by a stretched exponential profile. At 36 degrees C and higher temperatures, a new relaxation mode in the form of a power law enters at intermediate times, between the exponential and stretched exponential domains. The power law part of the relaxation function has its maximum time window at 37 degrees C (incipient gel) where it covers a time region of more than 3 orders of magnitude. The power law exponent is generally close to 0.5, except at the lowest temperature (36 degrees C) of power law behavior, where it is close to 0.6. A relaxation exponent of 0.5 can be rationalized within a framework of the fractal model for polymer networks. When the oscillatory shear data are transformed into equivalent shear stress relaxation data, they are shown to be compatible with the experimental shear stress relaxation data at all temperatures.