This package implements the earthquake ground motion prediction equations developed as part of the Next Generation Attenuation of Ground Motions (NGA) project coordinated by the Pacific Earthquake Engineering Research Center (PEER) in 2008. The models implemented in this package are AS08 (Abrahamson & Silva, 2008), BA08 (Boore & Atkinson, 2008), CB08 (Campbell & Bozorgnia, 2008), and CY08 (Chiou & Youngs, 2008). This numerical implementation has been validated by comparing the results for 128,000 test cases against the results obtained using the Fortran implementation composed by David M. Boore and Kenneth W. Campbell. Users are encouraged to view U.S. Geological Survey Open-File Report 1296, entitled "Implementation of the Next Generation Attenuation (NGA) Ground-Motion Prediction Equations in Fortran and R," by J. Kaklamanos, D. M. Boore, E. M. Thompson, and K. W. Campbell (2010) for further details on these programs. More details (including a change log) are available at <http://geohazards.cee.tufts.edu/people/jkakla01>.