Chemical mechanical polishing of tantalum was performed using alumina and silica particles dispersed in deionized water as a function of pH and ionic strength. The highest polish rate was obtained at pH values of 3.5 and 8.0 in silica and alumina slurries, respectively. The variation in the polish rate with pH is due primarily to variations in electrostatic interactions between the particles and the tantalum surface and the effect of changes in average particle size appears to be small. This is confirmed by the measured changes in tantalum polish rate due to changes in ionic strength of the slurry.