Listeners outperform automatic speech recognition systems at every level, including the very basic level of consonant identification. What is not clear is where the human advantage originates. Does the fault lie in the acoustic representations of speech or in the recognizer architecture, or in a lack of compatibility between the two? Many insights can be gained by carrying out a detailed human-machine comparison. The purpose of the Interspeech 2008 Consonant Challenge is to promote focused comparisons on a task involving intervocalic consonant identification in noise, with all participants using the same training and test data. This paper describes the Challenge, listener results and baseline ASR performance.