ARIA (Ambiguous Restraints for Iterative Assignment) is a software package by Michael Nilges for automated NOE assignment and NMR structure calculation. It uses an iterative structure calculation scheme and the final refinement in explicit water improves the quality of the calculated structures. More information and a manual about ARIA can be found on the ARIA website and on the ARIA discussion group on Yahoo. The ARIA software bundle, as implemented in this webportal is free for academic and educational purposes. The webportal is based on the ARIA version 1.2 package with several modifications (HJ development version).