The efficiency of implantable stimulation systems depends in large proportion of the electrode-tissue interface condition and in the choice of appropriate stimuli waveform. In this paper, we present an integrated flexible stimuli generator dedicated for high current stimulation in large electrode-tissue contact impedance. The system, powered by a single 3.3 V supply level, includes an integrated high voltage generator in order to supplies the output stage with -10 V/+10 V. High voltage parts are implemented in a 9 mm2 chip using a 0.8 um high voltage process. For area and power efficiency concern, the control unit of the whole device is implemented in a standard 0.18 um technology and use 1.96 mm2 of silicon area. Preliminary results indicate that the stimuli generator can deliver a stimulating current of 2 mA in electrode-tissue impedance as high as 9.125 kOmega.