The material presented in this book is intended to provide the reader with a practical treatment of Weibull distribution as applied to radar systems. Topics include general derivation of Weibull distribution, measurements of Weibull-distribution clutter, comparison of Weibull distribution including Rayleigh, gamma, log-normal and k- distributions, constant false alarm rate (CFAR) detectors for Weibull clutter, non-parametric CFAR detectors, and signal detection in the time and frequency domains. In particular, the Akaike information Criterion (AIC), which is a rigorously mathematical fit of the hypothetical distribution to the data, is emphasised.