Intraosseous (IO) infusion methods have been common for emergency treatment in infants and children for years. The role of IO access in adults is however much less clear, but its importance in this patient group is increasing, and different devices are available today. Each device has strengths and weaknesses, but all achieve rapid vascular access even in challenging situations. The potential of IO access regarding both therapeutic and diagnostic options has been shown in several operational studies in and out of hospital. Insertion times require between 1 and 2 min in most cases, while insertion and handling of the IO access devices seem to be easy and reliable. The flow rates of IO access devices for adults are lower than those of large-bore peripheral intravenous catheters, but fluid resuscitation is possible in most cases at least with pressure bag infusion systems. Most drugs administered intravenously can be given intraosseously in equivalent dosages and with the same effects. Nevertheless the limitations and risks of IO access routes need to be considered for each application. Rapid IO access is now possible in all age groups, and the 2005 AHA Guidelines favor it over drug administration via the endotracheal tube.