ABSTRACT The development of the concepts within 3DVIEWNIX and of the software system 3DVIEWNIX itself dates back to the 1970s. Since then, a series of software packages for Computer Assisted Visualization and Analysis (CAVA ) of images came out from our group, 3DVIEWNIX released in 1993, being the most recent, and all were distributed with source code. CAVASS , an open source system, is the latest in this series, and represents the next major incarnation of 3DVIEWNIX . It incorporates four groups of operations: IMAGE PROCESSING (including ROI , interpolation, filtering, segmentation, registration, morphological, and algebraic operations), VISUALIZATION (including slice display, reslicing, MIP , surface rendering, and volume rendering), MANIPULATION (for modifying structures and surgery simulation), ANALYSIS (various ways of extracting quantitative information). CAVASS is designed to work on all platforms. Its key features are: (1) most major CAVA operations incorporated; (2) very efficient algorithms and their highly efficient implementations; (3) parallelized algorithms for computationally intensive operations; (4) parallel implementation via distributed computing on a cluster of PCs; (5) interface to other systems such as CAD/CAMsoftware, ITK , and statistical packages; (6) easy to use GUI . In this paper, we focus on the image processing operations and compare the performance of CAVASS with that of ITK . Our conclusions based on assessing performance by utilizing a regular (6 MB), large (241 MB), and a super (873 MB) 3D image data set are as follows: CAVASS is considerably more efficient than ITK , especially in those operations which are computat ionally intensive. It can handle considerably larger data sets than ITK . It is easy and ready to use in appli cations since it provides an easy to use GUI . The users can easily build a cluster from ordinary inexpensive PCs and reap the full power of CAVASS inexpensively compared to expensive multiprocessing systems which are less efficient for CAVA operations. Keywords : visualization, 3D imaging, software systems, image analysis