Two modules of the L3 Silicon Microvertex Detector (SMD) have been tested on beam. The active area of the modules consists of double sided silicon microstrip detectors; the implantation pitch is 25 μm and 50 μm in the junction and ohmic side, respectively. The detectors are read out by a VLSI radiation hard amplifier (SVX-H). The position resolution, with a readout pitch of 50 μm and 200 μm for the two sides, is determined to be 7.0 μm and 14.3 μm. A signal to noise ratio ⩾ 16 and a detection efficiency ⩾ 99% are measured for both sides.