Thomas Huxley is often identified as the originator of the doctrineknown as ``epiphenomenalism,'' but there appears to be littleappreciation for the details of Huxley's theory. In particular,conflicting interpretations show that there is uncertainty about twoaspects of his position: whether mental states are completelywithout causal powers or simply have no influence on the behavior theyare typically taken to explain, and whether conscious epiphenomena arethemselves physical states of the brain or immaterial items. I clarifythese issues and show that Huxley's brand of epiphenomenalism is in factdifferent from the forms usually attributed to him.