The Atlantic THORPEX Observing System Test (Atlantic-TOST) trialed the real-time quasi-operational targeting of observations using a number of platforms (Including AMDAR, ASAP ships, extra radiosonde ascents, research aircraft, and meteorological satellites). To do this, it is necessary to identify suitable cases for targeting, provide information on the location of sensitive areas, and have the facilities to deliver extra observations within these areas at short notice. The Atlantic-TOST was the first time that the real-time adaptive control of such a complex set of observing platforms has been attempted. It is considered to be an essential preparation or 'proof of concept' for future targeting field campaigns. An overview of the TOST will be given and evaluation plans discussed.