Based on many years of laboratory experience in in-situ infrared catalytic research, ISRI has developed an in-situ IR-reactor capable of operating at high pressure (15 atm) and vacuum (10-5 torr). The IR-cell reactor design allows for the transmission IR data collection under flow or static conditions from room temperature up to 450oC. The low volume reactor is equipped with exchangable windows to cover a wide range or IR frequencies. The catalyst wafer is placed in a holder which has two heating elements to control the sample's temperature without heating the reactor's walls, thus avoiding problems related to the expansion of gasket material. The reactor can be fitted easily in most sample chambers of commercially available IR spectrometers.