Summary Based on our experience of 102 clinical cases and 100 anatomical dissections, we have assessed the indications for the posterior interosseous flap in reconstruction of the hand. Large fasciocutaneous island flaps can be harvested, even when the radial or ulnar pedicles are damaged. One real advantage is that the posterior interosseous artery is a vessel of secondary importance for hand vascularisation. Fasciocutaneous and osteofasciocutaneous island distally based flaps can be tailored. The major indications are reconstruction of the first web space up to the interphalangeal joint of the thumb, dorsal hand defects up to the metacarpal joints and large defects on the palm-ulnar border of the hand. It is, therefore, a primary weapon amongst hand reconstruction techniques.