This article describes the Uplug-system, a modular software platform intended for the integration of text processing tools. It includes three components: An extensible I/O library which provides a transparent interface for working with textual data, a tool for combining single-task text and corpus processing modules into sequentially executable systems, and a graphical user interface for running Uplug applications, modifying parameter settings, and investigating resulting data. The system supports a variety of storage formats, including those of standard database management tools such as SDBM and GDBM as well as simple XML formats and other text oriented data formats. Furthermore, connections to relational databases are supported via a transparent database toolbox. Uplug applications can be adjusted easily by modifying standardised configuration files. A prototype of the Uplug-system is currently used in a Linux version at Uppsala University with modules for processing bilingual parallel text, such as modules for several kinds of word alignment and data generation from parallel texts, as well as tools for the examination and evaluation of the results that are produced.