Cholesterol oxidase (ChOx) was covalently immobilized onto the woven silk fiber (silk mat) produced by Antheraea assamensis. The immobilization was done using N-ethyl-N'-(3-dimethylaminopropyl) carbodimide and N-hydroxysuccinimide ligand chemistry. The attachment of ChOx to the silk mat was demonstrated by scanning electron microscopy and activity study. The kinetic studies of the immobilized ChOx were performed by using a biological oxygen monitor. The enzyme loading was found to be 0.046 U cm(-2) of silk mat and the enzyme loading efficiency of the silk mat was estimated to be 70%. Remarkably high storage and operational stability (t(1/2) of initial activities) corresponding to 13 months and 25 numbers of assay (for a period of 6 h), respectively, of the fabricated ChOx electrode were demonstrated.