Abstract: A technique has been developed for obtaining reproducible viscometric data on dilute clay suspensions using the recently developed capillary viscometer of Maron, Krieger and Sisko. Aging and type of mixing have important effects on the viscosity of the dispersions. Attapulgite, hectorite, and Wyoming bentonite exhibit non-Newtonian behavior at all concentrations studied. The effect of temperature on the reduced fluidities of suspensions of the three clays is negligible. In this respect they agree with the behavior predicted for suspensions of rigid, noninteracting particles.