The rheological behavior of PVC plastisols that vary in volume fraction of resin from 0.567 to 0.670 was studied. Different particle‐size “cuts” from Tenneco Chemicals, Inc.'s 1730 dispersion‐grade‐poly(vinyl chloride) resin and di‐2‐ethylhexyl phthalate (DOP),n‐butyl benzyl phthalate (BBP), and di‐2‐ethylhexyl adipate (DOA) plasticizers were used to prepare the plastisols. In the range of concentration studied, both shear‐thickening and shear‐thinning behaviors were observed. In all cases discontinuous‐viscosity behavior was observed at a critical shear rate. The shear rate at which this viscosity discontinuity occurred depended strongly on the particle‐size characteristics of the resin and the compatibility of the plasticizer with the resin. This study has led to the following contributions:1. An experimental blending technique was developed that permits the determination of the maximum volume fraction of resin which will produce a fluid plastisol. This maximum volume fraction of resin,φMIX,is related to the particle‐size characteristics of the resin and the compatibility of the plasticizer with the resin.2. The resin content of the plastisols studied was expressed in terms of a reduced volume fraction,φR,that was calculated with the following compositional mixing formula:φR=∑i=1n∑j=1mxiyj (φ/φMIX ij),wherexi=volumefraction of theithliquid phase,yj=volumefraction of thejthsolid phase,φ=totalvolume fraction of resin(s)n=numberof plasticizers,m=numberof resins, andφMIX ij=φMIXof theithplasticizer with thejthresin. Since this expression involved only the determination ofφMIXfor each resin/plasticizer combination,φRcan be easily determined for variations in both the content of resin and the relative amounts of plasticizers and/or resins present in multiple‐component plastisols.3. A correlation was developed that relatesφRto the shear rate,γ̇d,at which the viscosity discontinuity occurs. The correlation equation,log10γ̇d=−9.8568+10.437/φR,was shown to be valid for values ofφRbetween 0.87 and 1.00. The above expression was also found to describe discontinuous‐viscosity behavior published by another investigator who used different resins. This model can be used as an aid in designing plastisols for specific flow properties.