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 formulation 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(upsilon, 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(upsilon, 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.