We present in this article a specialized suite of image processing programs primarily aimed at obtaining the three-dimensional reconstruction of biological specimens from large sets of projection images obtained by transmission electron microscopy. The programs are written in ANSI-C and use X-Windows for graphical output. A number of parallel extensions using PVM and PARMACS are provided. The programs are freely available by anonymous ftp at ftp.cnb.uam.es. (C) 1996 Academic Press, Inc.