The Cross-track Infrared Sounder (CrIS) is a key NPOESS sensor providing two environmental mission Key Performance Parameters (KPP) namely, the atmospheric moisture and temperature profiles. This presentation discusses the performance of the first CrIS flight instrument, which is a critical payload for the NPOESS Preparatory Project (NPP) mission. It describes instrument radiometric performance such as calibrated spectral response shape, error residuals and absolute spectral calibration of the CrIS Flight Model 1 (FM1) sensor including the signal processing algorithms used to radiometrically and spectrally calibrate the CrIS sensor. This includes a description of the CrIS on-board interferogram processing and the ground algorithms that convert Raw Data Records (RDR) into calibrated Sensor Data Records (SDR) and the Environmental Data Records (EDR). The SDR algorithm flow is given along with examples of the algorithm's ability for response linearity correction to radiometrically correct and produce ideal spectral response functions in all sensor Field Of Views (FOV) and spectral channels. In this presentation, sensor testing results will be summarized and both SDR and EDR performance will be discussed for the as-delivered CrIS sensor.