An improved group contribution method for the estimation of the normal boiling point of non-electrolyte organic compounds was developed using experimental data for approximately 2850 components stored in the Dortmund Data Bank (DDB). The new model is based on a me published earlier, which was extended using a steric parameter, additional corrections and group interaction parameters as well a: several additional groups for extended range of applicability. The mathematical formalism was modified to allow for separate examination and regression of individual contributions. The results of this separate examination lead to the detection of unreliable data and the definition of further structural groups. For the boiling point prediction, only the molecular structure of the compound is used. The results of the new method are compared to the previous work and several currently used methods and are shown to be far more accurate and reliable. The detailed comparison for a large number of different sets of chemically similar compounds allows one to access the probable estimation error of the different methods. Structural groups were defined in a standardized form and fragmentation of the molecular structures was performed by an automatic procedure to eliminate any arbitrary assumptions. (C) 2004 Elsevier B.V All rights reserved.