The current measured during the back step of a double potential step chronoamperometry experiment at microvoltammetric electrodes is primarily nonfaradaic and can be used for residual current correction. An instrument has been designed which provides direct readout of the corrected current. This instrument also provides differential output and adjustable delay and step times which can be important for the unusual conditions ofinvivovoltammetric experiments. All of these features are tailor made for use with microvoltammetric electrodes and are unavailable in commercial instrumentation. Experimental results indicate that potential step times as short as 100 ms can be used with back step correction with a faradaic accuracy of better than 5%. Pulse scans are compared to conventional cyclic voltammetry in the reduction of 5×10−5M potassium ferricyanide.