Abstract: Deflocculation state was considered to be necessary for better fluidity and spreadability of barium sulfate suspension taken as an X-ray contrast medium in the examination of gastro-intestinal tract. The Zeta-potential of the barium sulfate particles in increasing. concentration of different electrolytes was measured by the eletrophoretic method in a Burton Cell. The results were compared with the corresponding sedimentation volume. It was found that the Zeta-potential ranging from 50 mV to 66 mV favored the deflocculation of the suspension, while that below 22 mV, flocculation was affected. The viscosities of 100%, 130% and 150% barium sulfate suspensions were measured using Hoppler's Rheo-viscometer. The viscosity dropped quickly at first on the addition of electrolytes, and then increased to some extent with further increase of electrolyte concentration. The minimum viscosity was considered to reflect complete deflocculation of the suspending particles. The electrolyte concentration producing minimum viscosity was shown to be the most effective deflocculating agent tested, while sodium pyrophosphate and sodium citrate are less effective.The flocculation of the barium suspension by the gastric fluid after ingestion often leads to some troubles to the roentgenologists. We examined the ability of different electrolytes to retard such flocculation by means of the viscosity method.