Abstract The kinetics of crystallization of barium sulphate for both seeded and unseeded systems in presence of additives have been studied by following the changes in ionic conductivity in supersaturation solutions containing stoichiometric concentrations of the lattice ions at 298 K. The additives investigated include: 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), hexa methylenediaminetetramethylenephosphonic acid (HMNTMP), ethylenediaminetetramethylenephosphonic acid (ENTMP) and nitrilotrimethylenephosphonic acid (NTMP). The effect of these additives on the growth kinetics has been studied at several inhibitor concentrations. The retarding effect of these inhibitors is interpreted in terms of adsorption of inhibitor ions at the active crystal growth sites following the Langmuir isotherm. The order, in terms of decreasing the inhibitory effect on the rate of growth of barium sulphate of the studied additives is HEDP > HMNTMP > ENTMP > NTMP. This order holds for both seeded and unseeded systems.