As part of a research effort to obtain an understanding at a fundamental level of the oxidation of Ni, in situ near normal incidence UV-visible spectroelectrochemistry has been us ed to study the pro cess in aerated phosphate solutions at pH 5.4. The variation of film thickness with applied potential has been studied. At potentials preceding that of the passive region, the surface film is found to consist primarily of Ni(OH)(2). In the passive region, the surface film consists of both Ni(OH)(2) and NiO. Reasonable estimates of passive film thickness can be obtained by this methodology. It is demonstrated that the exact sequence of potentials utilized in the oxidation of the Ni electrode has a bearing on film growth.