During fast-scan cyclic voltammetry (FSCV), the electrical potential of the carbon fiber microelectrode (CFM) is rapidly scanned to generate a voltammogram, which resolves individual chemicals on the basis of redox potential, kinetics and reversibility. The voltammogram, coupled with high temporal resolution, render FSCV at a CFM, a powerful technique for monitoring neurochemicals. In the present project, a dual microsensor consisting of two disks is constructed by pulling two carbon fibers, aspirated and sealed with epoxy in theta glass, and polishing the tip. One disk is untreated and used with FSCV to monitor the neurotransmitter dopamine, oxygen and pH. The second disk, a pH sensitive potentiometric probe, is developed by depositing iridium oxide on the carbon fiber. While FSCV at a CFM has previously been used to monitor pH, only measurements evoked by electrical stimulation have been verified independently using a separate sensor (e.g., ion selective microelectrode). Hence, one rationale for the dual microsensor design is to facilitate the verification of voltammetric monitoring of pH in different applications. Once verified, the second half of the dual microsensor could be develop for other measurement schemes. Flow injection analysis was used to characterize the pH sensing probe to determine sensitivity over a physiological range and selectivity to sodium, potassium, calcium and chloride, ions potentially interfering with pH measurements in the brain. The bare CFM will be evaluated for dopamine measurements. Future applications include simultaneous measurement of striatal dopamine, oxygen and pH in the intraluminal thread model of focal ischemia, a rat model of stroke.