Recent developments in the use of non-intrusive, electrical measurements to interrogate mixing processes in batch vessels have triggered a joint GSK/Imperial College London project aimed at assessing the applicability of electrical resistance tomography (ERT) to pharmaceutical chemical development. Several vessel/stirrer configurations designed to mimic typical plant reactor geometries were investigated in connection with multiphase processes typical of the pharmaceutical industry. Case studies related to liquid-liquid dispersion and solids suspension in stirred tanks are described and the data obtained are compared with on-line monitoring information as well as computational fluid dynamics modelling results. Overall, very encouraging results were achieved for model and industrial processes. This approach shows promise for on-line control of process mixing performance as well as efficiency evaluation and optimization of several reactor geometries. This allows us to conclude that ERT is a valuable tool for the development of robust active pharmaceutical ingredient (API) manufacturing processes.