Hops and hop oils are known to be a source of flavour-potent organosulphur compounds in the brewing process. In the past, relatively little information has been discovered concerning the actual compounds responsible, and what factors are involved in their formation. However, most of. the major sulphur compounds normally present in hop oil have now been chemically characterised. Furthermore it has been found that the spectrum of organosulphur volatiles derived from hops is affected by treatments that hops receive with elemental sulphur on the bine and with sulphur dioxide during hop drying. Treatment of hops with elemental sulphur leads to ready formation, in the essential oil, of several dimethyl polysulphides and some novel terpene/sulphur adducts, including episulphides of humulene and caryophyllene and a series of sulphur-containing heterocycles derived from myrcene. Treatment of hops with sulphur dioxide during drying has been shown to result in steam distilled hop oils containing diminished levels of dimethyl trisulphide. A mechanism is proposed which accounts for this phenomenon and also for the observation that the initial effect of the sulphur dioxide gradually becomes nullified when treated hops are stored for prolonged periods of time, Many of the newly identified sulphur-containing components of hop oil have been chemically synthesised, and added to beer for flavour evaluation. The compounds have flavour threshold values ranging from 0. 1 ppb to 1.8 ppm, and are generally considered by tasters to have a deleterious effect on beer flavour. A method has been developed which is suitable for the concentration and gas chromatographic estimation of traces of sulphur compounds occurring in beer. Using this technique several hop-derived sulphur compounds may be readily detected when added to beer at or below their respective flavour threshold concentrations.