The SEE Software Engineering Environment is a practical, portable, software development environment whose tools and concepts are nearly independent of the edited programming language and the supporting host editor environment. The SEE environment is a software engineering environment which manipulates components of the software lifecycle, in contrast to programming environments which manipulate structured programming languages. Three prominent features of SEE which distinguish it from other environments are the use of a standard software module structure to support lifecycle-oriented software tools, the use of source code as a vehicle for the collection and analysis of project size and time cost data, and the use of tools which preserve the developer's mental train of thought and display screen context. SEE supports the four major project activities of design, implementation, documentation, and project management by providing tools and procedures which simplify or automate many common tasks. The portability of the SEE environment is evaluated based on experiences gained in moving the core of the original environment from a Lisp-based mainframe editor to a C-based microcomputer editor, and the utility of the environment is evaluated on the basis of several commerical, institutional, real-time and application projects.