The behaviour of the leakage current, interstrip resistance and capacitance have been studied on silicon microstrip detectors during an annealing period equivalent to C10 8 min at room temperature, after 34 MeV proton irradiation. A comparison between samples of the same geometry built on /1 0 0S and /1 1 1S substrates with different resistivity has been carried out. The samples were irradiated at 4 different fluences up to 1 Â 10 14 p=cm 2 : After the irradiation the measurements were performed at room temperature and after heating the samples at 60 C; 80 C and 120 C to cover the complete annealing curve. The leakage current shows the same annealing behaviour typical of a simple diode. The interstrip resistance measured at full depletion voltage ðV dep Þ decreases in all structures, going down to few tens of MO at the highest fluence. It remains practically constant during the annealing period. The interstrip capacitance (at V dep ) varies during the annealing period with the same behaviour in both substrates and for all the fluence values: it decreases during the annealing at room temperature, reaching a minimum value, and increases after each heat treatment. Bistable defects seem to contribute to the interstrip capacitance variation.