ADAPT 5 represents a major new version of ADAPT with expanded capabilities and other enhancements, including Parametric population PK/PD modeling using maximum likelihood estimation via the EM algorithm (MLEM module) as introduced by Schumitzky (1995) and Walker (1996), with enabling computational enhancements and extensions by Bauer and Guzy (2004). In addition, ADAPT 5 includes Iterated two-stage (ITS) analysis as proposed by Prevost (1977) and Steimer, Mallet and colleagues (1984), as well as convenient standard two-stage (STS) and naive pooled data (NPD) modeling, each with WLS, ML and MAP estimator.