The RVI has been proposed as a method for monitoring the level of vegetation growth, particularly when time series data are available. However, few studies have attempted to establish a relationship between RVI and biophysical variables [12]. In this letter, we analyze the relationships between the RVI for a variety of relevant configurations (L-, C-, and X-bands) and crop growth parameters (VWC, LAI, and NDVI) over an entire rice and soybean growth cycle. The RVI is given by