A simple method for rapid determination of trace Au in natural water was presented by using UV-vis spectrophotometry after reaction of gold (III) with 3,3', 5,5'-tetramethylbenzidine hydrochloride (TMBH) in acidic solution. Under the optimum conditions, in a concentration range of 100-2000 mu g L(-1) of Au (III) a good linear calibration graph was obtained (r = 0.9969, n = 7). The percent relative standard deviation (RSD) for determination of 1000 mu g L(-1) Au was 10% (n = 3) and limit of detection based on a signal-tonoise ratio (S/N) of 3 (3S(bl)) was 50 mu g L(-1). The proposed method has been successfully applied to the determination of gold spiked and real aqueous samples. (C) 2008 Elsevier Ltd. All rights reserved.