Overcrowding in the emergency department (ED) has become an increasingly significant worldwide public health problem in the last decade. It is a consequence of simultaneous increasing demand for health care and a deficit in available hospital beds and ED beds, as for example it occurs in mass casualty incidents, but also in other conditions causing a shortage of hospital beds. In Italy in the last 12-15 years, there has been a huge increase in the activity of the ED, and several possible interventions, with specific organizational procedures, have been proposed. In 2004 in the United Kingdom, the rule that 98 % of ED patients should be seen and then admitted or discharged within 4 h of presentation to the ED ('4 h rule') was introduced, and it has been shown to be very effective in decreasing ED crowding, and has led to the development of further acute care clinical indicators. This manuscript represents a synopsis of the lectures on overcrowding problems in the ED of the Third Italian GREAT Network Congress, held in Rome, 15-19 October 2012, and hopefully, they may provide valuable contributions in the understanding of ED crowding solutions.