This paper presents design, fabrication, and testing of a microscale ceramic reactor for the pyrolysis of organic compounds. One application for this pyrolysis reactor is to convert the oxygen and hydrogen atoms in organic compounds to CO and H-2 for isotope ratio measurements in a continuous flow mode. Existing commercial pyrolyzers use high carrier gas flow rates (typically 80-100 mL/min) such that >95% of the CO and H-2 produced from a given sample is vented before introduction into the mass spectrometer. We describe here the fabrication and testing of a microscale pyrolysis reactor designed to be compatible with existing isotope ratio mass spectrometers. The microreactor uses carrier gas flow rates of 3-5 mL/min, decreasing the proportion of the CO and H-2 lost in venting and permitting analysis of samples 20-50 times smaller than can be analyzed with conventional pyrolysis reactors. Results have shown that organic compounds, such as 1-butanol, ethanol, and ethanolamine, can be fully decomposed to desired products CO and H-2, at a temperature of 1200 degrees C, which is 200 degrees C lower than conventionally reported. Furthermore, we are able to eliminate undesired products such as methane and CO2 in the pyrolysis process. The proof-of-concept experimental results clearly demonstrate that the micropyrolyzer quantitatively converts organic compounds to gases suitable for isotope ratio analysis.