Ceramic-polymer composite thermistors using superconducting YBa2Cu3O7-x powder have been fabricated. Percolation and subsequent positive temperature coefficient (PTC) of resistance effects are observed for all the composites. Results indicate that percolation and PTC behaviour are related to the powder characteristics, composite microstructure and ceramic-polymer interface. The reproducibility of the resistivity - temperature behaviour for the polyethylene composites upon thermal cycling is illustrated and is found that the location of the PTC transition is independent of the number of thermal cycles. However, the room temperature resistivity increases by about 1 order of magnitude from the first to the forth cycle. Composite thermistors with room temperature resistivity as low as 1cm and 11 order of magnitude change at 1kHz were achieved.