INQUA's life-blood is its national and regional members and many thousands of scientists from around the world. Member states extend throughout the Americas and from Australasia to Europe.

Group Membership in any country or geographic region may be assumed by any one of the following bodies - the National Academy, the National Research Council, a similar institution, or an association or group of scientific institutions or societies.

After admission each Group Member forms a National or Regional INQUA Committee to represent it in the affairs of the Union.

Each Group Member appoints one Group Delegate to the International Council of the Union, where the Group Delegate has the right to vote, provided the current subscription of the Group Member has been received by the Treasurer.