Novel epoxy-based organic/inorganic hybrid materials filled with carbon black (CB) were synthesized from an epoxy resin and silane alkoxide via a sol-gel process. The phase structure and thermal and mechanical properties of the hybrid materials were studied in detail. It was revealed by transmission electron microscope observations that the filled CB particles formed a secondary aggregation structure and were uniformly dispersed in the aggregate. The storage modulus in the rubbery region increased and the peak area of the tan delta curve in the glass-transition region decreased with the hybridization of silica. Moreover, the conductive properties of the CB-filled hybrid systems were investigated. In the same volume fraction of CB, the conductivity of the hybrid systems was much higher than that of the unmodified system. This result was attributed to the excluded volume effect of the silica network. (C) 2003 Wiley Periodicals, Inc.