This workshop addressed the issue of treatment in propionic acidaemia (PA) and methylmalonic acidaemia (MMA) and in particular the outcome of conventional management compared with organ transplantation. Although it appears that with medical treatment the mortality for early-onset disease has improved, long-term outcome remains poor. However, liver and liver/kidney transplantation is associated with a high perioperative mortality and long-term complications. It offers only a partial cure. The indications for transplantation remain unclear. It is recommended that a register of PA and MMA patients should be established.