The present paper deals with an application of the ultrasonic attenuation technique to evaluate slurry characteristics. Ultrasonic attenuation coefficients were observed for commercial-grade alumina powders with different dispersion/agglomeration conditions controlled by the amount of dispersant added or the pH adjustment. For slurry with relatively low solids content, attenuation increases linearly with an increase in the attenuation distance, suggesting that interaction forces between particles does not play an important role in the attenuation behavior. Experimental results for slurries with high solids content, however, reasonably demonstrated that changes in ultrasonic attenuation should be caused by the interaction forces. A methodological measurement of the amount of attenuation confirms that the ultrasonic attenuation behavior would be mainly affected by the boundary conditions between the particle surface and the surrounding dispersion medium, not by the dynamic conditions at contacts of particles.