We compare laboratory measurements of wave propagation and attenuation in grease ice with two viscous fluid models. The first is the classic infinite depth, constant viscosity one-layer model. The second is a new finite depth two-layer model developed by Keller in which the upper layer (grease ice) is a constant viscosity, immiscible fluid overlying a denser but inviscid lower layer (seawater). In our comparison of these models with the laboratory results, we use the viscosity v as a free parameter and search for that v which gives a best fit to the data. The results of this calculation show that the two-layer model, with a grease ice viscosity 2-3¿104 that of seawater, provides the best agreement of data with theory. Because the 0.1 m thickness of our laboratory grease ice is comparable to thicknesses observed in the polar oceans, the Keller model with this viscosity value should be directly applicable to the field interaction of waves and grease ice. ¿ 1999 American Geophysical Union