Non-Faradaic electrodeposition of polyborate monolayers at Agr(111) in aqueous solutions containing sodium berate (Na2B4O7) is reported. Electrodeposition is characterized by a very sharp voltammetic wave with half-wave potential E-1/2 approximate to -1.2 V vs Hg/Hg2SO4 and surface charge density sigma 20 +/- 5 mu C/cm(2). X-ray photoelectron spectroscopy and electrochemical quartz crystal microbalance measurements demonstrate that monolayer formation occurs at potentials positive E-1/2. The voltammetric behavior suggests that electrodeposition is associated with the polymeric condensation of B(OH)(4)(-) and B(OH)(3), both species produced by the dissociation of B4O72- in the bulk solution (B4O72- + 7H(2)O reversible arrow 2B(OH)(4)(-) + 2B(OH)(3)). The dependence oi : the voltammetric wave shape on scan rate is consistent with the nucleation and growth of an ordered polyborate monolayer. Deposition of the monolayer is also observed in boric acid/NaOH solutions, strongly supporting the proposed mechanism.