A systematic investigation has been carried out on the tilt and azimuth angle dependencies of output characteristics of photovoltaic modules. The measurements have been made on some combinations of two prototype modules of poly-Si solar cells, installed at different tilt angles and azimuth angle. Output parameters were measured in the form of I-V characteristics. The analysis of the results shows that: (i) provided output voltage is appropriate to the system operation, no serious problems are likely to arise out of the parallel connection of two modules at different tilt and/or azimuth angles, if protected by blocking diodes; and (ii) in the case of series connection equipped with by-pass diodes, however, the max-power voltage (Vmp) becomes instable if the azimuth angle is 15 degrees or more different from each other. That is because the Vmp drops down to the Vmp level of the higher output-current module.