Abstract : The ultramicroelectrode ensembles yield responses which are in quantitative agreement with predictions of established electrochemical theory. Furthermore, a one order of magnitude improvement in detection limits (relative to a conventional, macro-sized electrode) is demonstrated. In a recent correspondence, we described a new procedure for preparing ultramicrodisk electrode ensembles; the ultramicrodisks were formed by filling the pores of a microporous host menbrane with carbon paste. In this paper we present results of quantitative and semi-quantitative analyses of the electrochemical response characteristics of these ultramicroelectrode ensembles; we show that the responses are in agreement with predictions of established electrochemical theory. We also show that one of the ensembles investigated here can yield electroanalytical detection limits which are order of a magnitude lower than detection limits at an equivalent macro-sized (0.331 sq.cm.) electrode. Ultramicrodisk electrode, Electrochemical response, Electroanalytical detection limits.