SpeechLex is a module of an experimental speech recognition system. The main features of this system axe the rule-based approach for the acoustic-phonetic detection, the incorporation of Fuzzy Logic to handle uncertain decisions, and an overall top-down recognition strategy. The task of SpeechLex is to set up a phonotactical network describing the words of a given vocabulary with common variations in pronunciation and to drive the acoustic-phonetic rules of another module. Processing is, in principle, carried out left-right, i.e. one syllable after the other, but inside-out within a syllable. Since the whole system is of an experimental nature, emphasis was laid on providing it with graphical aids to trace the processing steps and to support its development.