A rapid and versatile method for the determination of sulphur in biological materials based on the stoicheiometric combination of mercury(II) and sulphur(II) with an acetone-dithizone indicator is described. Although slightly less sensitive than some other micro methods it has a wide range and is less subject to interference.Precautions are suggested for total sulphur determination of samples with a high sulphate-sulphur concentration. Convenient procedures for the determination of total sulphur, total sulphate-sulphur, ester sulphate-sulphur, neutral sulphur and inorganic sulphate-sulphur are outlined, and also the possibility of combining liquid scintillation measurements of sulphur-35 with the same determinations.