Its aims are essentially historical, to encourage the study of Cromwell'slife and times and of the Parliamentary cause during the Civil War, Commonwealth and Protectorate. The Association also encourages the archaeological and architectural investigation of the physical heritage of the mid seventeenth century. The Association has a wide and varied membership, some living overseas, particularly America and Australasia, although naturally most are British based. Some members have a professional or academic involvement in seventeenth century history, but most are simply interested in the period. The Association is neither sectarian nor political and there is no minimum age limit.
Membership is open to all, upon payment of an annual or life subscription.
Members are encouraged to play an active role within the association and some form local groups for study or social purposes. The Association helped to establish and supports the Cromwell Musem in Oliver's former Grammar School in Huntingdon and has a continuing programme of erecting commemorative tablets at sites and buildings with Cromwellian or Parliamentary connections - amongst those already covered are the battlefields of Naseby, Dunbar and Marston Moor and buildings in Preston, Worcester and London. For example, the Association has been involved in attempts to preserve the battlefields of Naseby and Marston Moor and in the restoration and reopening of Cromwell's house in Ely. It also advises television, radio and the press on matters relating to the period. Members receive a scholarly annual journal, Cromwelliana , and regular newsletters.