Abstract: A concept recognition system includes a concept recognition training system and a real-time system. The concept recognition training system processes a training set and produces a lexical profile keyed to a target category. The lexical profile comprises a set of lexical cues, which are words and phrases associated with the target category. A trainer starts with an initial lexical profile that comprises a small set of seed cues. The training system retrieves samples from the training set that match lexical cues in the lexical profile. The trainer determines which of the retrieved samples are positive instances of the target category. The training system extracts lexical cues from the positive instances and adds new lexical cues to the lexical profile. The real-time system uses the lexical profile as the basis for making confidence judgments for each new incoming message from the same input stream with respect to whether the message is an instance of the target category.