Inorganic barium sulphate is probably the hardest type of scale to inhibit in oil and gas production pipelines due to its physical hardness chemical and thermal stability. Barium sulphate scale is most commonly inhibited by the use of phosphonate and polymeric scale inhibitors (SIs) deployed at sub-stoichiometric concentrations. What is much less well known in the oil industry is the effect of using combinations of SIs synergistically (i.e. more than one) for enhanced scale inhibition performance. Synergistic blends can yield mechanistic benefits. In this paper we present a series of static barium sulphate inhibition efficiency (IE) test results in which a series of “pairs” of SIs have been tested synergistically at pH 5.5 and 95oC (typical topside reservoir conditions). Polymers can be blended with phosphonates or alternatively; “pairs” of phosphonates or “pairs” of polymers may be applied. In all cases the synergistic IE is compared with the IE of each SI tested independently. Each “pair” of SIs have previously been tested separately for barium sulphate IE at pH 5.5 95oC over a range of [SI]s in order to determine the minimum inhibitor concentration (MIC) for each species (Shaw et al 2012). A total of 9 phosphonate and 9 polymeric SIs have been tested individually. The MICs of the synergistic blends are compared with the regular MICs of the individual SIs. We find that in most cases the synergistic IE is consistently higher over the range of [SI]s tested (i.e. MIC lower) compared to that of each SI tested separately. Only certain “pairs” of SIs used together yields a significantly beneficial effect (i.e. lowering of MIC; enhanced IE); e.g. DETPMP and HMTPMP.