We report our pioneering experimental investigation of polymer particle size and size distribution in suspension polymerisation of methylmethacrylate (MMA) in a batch 50 mm diameter stainless-steel jacketed oscillatory-baffled reactor. In such a reactor, fluid mixing is achieved by eddies that are generated when fluid passes through a set of equally spaced stationary orifice baffles. Those periodically formed vortices can be controlled by a combination of operational and geometrical parameters, such as oscillation frequency, oscillation amplitude, baffle diameter and baffle spacing. Based on a confidential and scaled-down fcormulation of a proprietary dental-grade MMA resin supplied by the Bonar Polymers, polymerisation reactions were performed under a controlled environment and the effects of the operational conditions on transient droplet size, final polymer particle size and their size distributions are studied. The mean particle size of polymer, d v,0.5 , is compared with the Sauter mean size of droplet, d 32, obtained with no reaction taking place and a correlation between d 32 and d v,0.5 is established, which predicts the final particle sizes of polymer being made in such a reactor with a high degree of accuracy. In addition, a comparison of polymer particle size distribution, molecular weight distribution and residual initiator content is also carried out between our reactor and the traditional stirred-tank reactor.