FEAR: Frontier Efficiency Analysis with R. FEAR consists of a software library that can be linked to the general-purpose statistical package R. The routines included in FEAR allow the user to compute, among other things, nonparametric estimates of technical, allocative, and overall efficiency while assuming either variable, non-increasing, or constant returns to scale. The routines are highly flexible, allowing measurement of efficiency of one group of observations relative to a technology defined by a second, reference group of observations. Consequently, the routines can be used to compute estimates of Malmquist indices, scale efficiency measures, super-efficiency scores, and other measures that might be of interest. Before using FEAR, one must download and install R. The R installation program and documentation for R can be found at the R website. R is distributed under the GNU General Public License Version 2. FEAR is distributed under the license that appears in the file named ”LICENSE” that is part of the FEAR package; click here to see the license before downloading the software or documentation. Downloading the FEAR software or documentation constitutes acceptance of the terms and conditions in the license.