The simple, fast and highly sensitive anodic stripping voltammetric detection of As(III) at a gold (Au) nanoparticlemodified glassy carbon (GC) (nano-Au/GC) electrode in HCl solution was extensively studied. The Au nanoparticles were electrodeposited onto GC electrode using chronocoulometric technique via a potential step from 1.1 to 0 V vs. Ag j AgCl j NaCl (sat.) in 0.5 M H 2 SO 4 containing Na [AuCl 4 ] in the presence of KI, KBr, Na 2 S and cysteine additives. Surfaces of the resulting nano-Au/GC electrodes were characterized with cyclic voltammetry. The performances of the nano-Au/GC electrodes, which were prepared using different concentrations of Na[AuCl 4 ] (0.05 -0.5 mM) and KI additive (0.01 -1.0 mM) at various deposition times (10 -30 s), for the voltammetric detection of As(III) were examined. After the optimization, a high sensitivity of 0.32 mA cm À2 mM À1 and detection limit of 0.024 mM (1.8 ppb) were obtained using linear sweep voltammetry.