Abstract Potassium bromate has been used as a redox reagent in the presence of potassium iodide for the visual and potentiometric determination of thiourea and its several alkyl and aryl derivatives in a sulphuric acid medium. In visual titrations, amylose, is used as a visual indicator, turning blue at the end-point. In the potentiometric method, a bright platinum wire is used as an oxidation-reduction electrode ; this is coupled with a saturated calomel electrode. The thioureas are oxidised to their corresponding disulphides with a single electron-change: (Remark: Graphics omitted.) This direct method is simple, accurate, instantaneous and widely applicable. One of the present authors (B. C. V.) wishes to thank the Council of Scientific and Industrial Research, Rafi Marg, New Delhi, for the award of a Senior fellowship.