This International Standard specifies a method for the determination of the styrene content of all types of styrene-butadiene rubber (SBR), including oil-extended types. The method is applicable to styrene-butadiene rubbers reinforced with styrene homopolymer, to give the total styrene content. The method is also applicable for determining the styrene in block copolymers containing up to 50 % (by mass) of styrene. It is applicable to vulcanizates of mixtures of SBR with other polymers (NR, BR, IR and CR) and is considered a method for estimating the SBR content of mixtures, if the styrene content of the SBR is known and provided that no other styrene-containing materials are present. Any other non-extractable aromatic material which absorbs in the specified spectral region will interfere with this method. The procedure may give low results when the content of mineral fillers insoluble in nitric acid exceeds 5 % (by mass).