Cyclone is a polymorphic, type-safe programming language derived from C@. The primary design goals of Cyclone are to let programmers control data representations and memory management without sacrificing type-safety. In this paper, we focus on the region-based memory management of Cyclone and its static typing discipline. The design incorporates several advancements, including support for region subtyping and a coherent integration with stack allocation and a garbage collector. To support separate compilation, Cyclone requires programmers to write some explicit region annotations, but uses a combination of default annotations, local type inference, and a novel treatment of region effects to reduce this burden. As a result, we integrate C idioms in a region-based framework. In our experience, porting legacy C to Cyclone has required altering about 8% of the code; of the changes, only 6% (of the 8%) were region annotations. This technical report is really two documents in one: The first part is a paper submitted for publication in November, 2001. The second part is the full formal language and type-safety proof mentioned briefly in the first part. If you have already read a version of, ``Region-Based Memory Management in Cyclone'', then you should proceed directly to Section 9.