A discrepancy in the results of the potential dependence of the chemical etch rate of (100) Si in alkaline solutions has been investigated. In contrast to previous work at high temperature, the etch rate of p-type silicon is found to be constant in the range negative with respect to the open-circuit potential while the etch rate of the n-type semiconductor decreases markedly. In line with some previous suggestions, this difference is accounted for by differences in the potential distribution at the semiconductor/solution interface, as revealed by electrical impedance measurements under etching conditions. The potential dependence of the anodic current, which is attributed to electron injection from an intermediate of the chemical etching reaction, is also considered.