This paper presents a high-voltage, high-current implantable cortical stimulation integrated circuit aiming at supporting rehabilitation of patients suffering from stroke. In this context, a large area of the motor cortex needs to be stimulated, requiring high current densities at the electrode-electrolyte interface. The designed integrated circuit contains eight fully programmable stimulation channels generating biphasic constant current pulses up to 8mA from a 20V supply. The current mismatch between positive and negative pulses has been evaluated at 0.03 per cent. The chip has been fabricated in a AMS 0.18m high voltage CMOS process, and has a die area of 5mm2.