The water vapour sorption behaviour of a range of sheep wool types and alpaca was studied using dynamic vapour sorption. Sorption isotherms have been interpreted using the polymer sorption model developed by Vrentas and Vrentas. Satisfactory fits were obtained for absorption and desorption isotherms with the adjustment of parameters outside of the scope of what is allowed. This is possibly because the underlying Flory-Huggins approach does not take into account any clustering of sorbate within the polymer. Water clustering in the wool fibre, determined using the Zimm-Lundberg clustering function, starts above a fibre moisture content of approximately 20%. Sorption kinetics was analysed using the parallel exponential kinetics model, providing excellent fits and allowed for calculation of a fibre modulus at different relative humidities; the values were reasonable at the upper end of the hygroscopic range, but were over-estimated at the lower end of the range.