St Benedict
Cistercian monks follow the Rule of St Benedict as this was interpreted by a reform movement initiated by St Robert, St Alberic, and St Stephen at the monastery of Cîteaux, France in 1098. Within a short period of time, monasteries following this renewal were found from Ireland to Hungary, and from Scandinavia to the Mediterranean, some being home to hundreds of monks, many attracted by the influence of St Bernard of Clairvaux and other spiritual giants of his generation.
 Sts Robert, Alberic, and Stephen
St Bernard of Clairvaux
A second reform, beginning in the seventeenth century, and associated with the abbey of La Trappe, re-asserted the importance of a full, balanced monastic life. Under the leadership of Armand de Rancé and others, they sought a greater fidelity to the Rule with its emphasis on prayer, community life, work, and separation from the world.  
Armand de Rancé
Today, the Strict Observance Cistercians or Trappists number more than 170 monasteries with about 2,200 monks and 1,800 nuns in every continent. Since 1950, there has been a period of great expansion, with about half of the monasteries founded in that time, especially in Africa, Asia, and South America. Many monasteries also offer the possibility of lay associates.
Mixed General Chapters, Assisi, September 2008