Release notes for Maxima 5.9.0: This is the first of a series of develoment releases which will culminate in Maxima 6.0, which will be the first truly stable release of the new Maxima project. This release has known bugs. However, we believe it is stable enough for use by a wide audience. We are relying on bug reports from users to help us make 6.0 the most bug-free version of Maxima ever. Changes in this release include: 1) Maxima is now compatible with ANSI Common Lisp. CMUCL, Clisp and GCL are fully supported. 2) Maxima has a new build system based on the GNU Autotools. Installation should be easier and more flexible than ever before. 3) The Maxima build now uses mk:defsystem from CLOCC at the Lisp level. mk:defsystem provides a powerful and familiar environment for Lisp developers. 4) Maxima has a new User Manual, which is provided as a complement to the detailed reference manual from earlier versions of Maxima. 5) The command-line interface has been enhanced with several options, including a batch mode. 6) The bundled Emacs/XEmacs modes have been improved. 7) The internal layout of source code and shared Maxima files has been vastly improved. 8) Precision of some numerical special functions has been dramatically enhanced. 9) Last, but not least, many bugs have been fixed.