The operating system's group at Technische Universit?t Dresden is pleased to announce the first draft of the L4.Sec Preliminary Microkernel Reference Manual. The document can be found at http://os.inf.tu-dresden.de/L4/L4.Sec/ L4.Sec is a specification of a next generation microkernel interface targeted to co-host user-level servers implementing security-critical functionality next to untrusted and potentially malicious software. Bernhard Kauer