High quality thin films of Bi2Sr2Ca2Cu3O10 with critical temperatures of 95K were used to prepare grain boundary Josephson junctions on commercial 36.8 degrees SrTiO3-bicrystal substrates. IcRn- products of 50 (mu) V at 77 K and 0.7 mV at 4.2 have been reached. For temperatures higher than 50K the current- voltage curves of the junctions can be well described by the resistively shunted junction model and show no hysteresis. From the hysteretic behavior at low temperature we estimate a junction capacitance of 21 (mu) F/cm2. The Fraunhofer pattern of the critical current in an external applied field shows, that the junctions are inhomogeneous on a micrometers scale. The SQUID modulation of a 30 X 40 micrometers 2 wide superconducting loop containing two 10 micrometer wide junctions yields a flux-voltage transfer function of 2.7 (mu) V/(Phi) 0 at 78K.