This award is support the porting of code of the software package SPIDER from its present VMS environment to a UNIX environment. The SPIDER package is a unique image processing system for electron microscopy which was developed by the principal investigator and his associates. This effort will make the new technology of single particle averaging, correlation methods, multivariate statistics, single-particle reconstruction and electron tomography available to a large circle of users. The strong interest among user groups in such a conversion is documented. The increased access of many user groups to this large resources will make a significant contribution to the fostering of Computational Biology.