1. The Commissions of the IUCr are formed to provide continuing or semi-permanent functions in areas of special interest, in contrast with the temporary activities of sub-committees of the Executive Committee. The Commissions are formed by the General Assembly and operate under provisions of the Statutes [1.2(d), 4.1(c), 5.10(d), 5.10(e), 5.10(g), 5.11(c), 5.11(d), 8.1, 8.2, 8.3, 8.4, 9.2, 9.9] and the By-Laws [1.2, 1.4, 3.2, 4.2, 5.2, 7.1, 7.2, 7.3, 7.4, 8.3, 8.4, 8.8]. The Commissions are working bodies organized to provide a useful service on some aspect of crystallography; their formation and continued existence is to be justified on this basis.

2. Members of Commissions are chosen as representatives of areas of interest and activity and not as representatives of countries. The members are elected by and are responsible to the General Assembly and not to National Committees. Membership is based on the availability of the person for rendering active assistance to the objectives of the Commission and not on the basis of his/her worthiness for honour.

3. The size of each Commission is determined by the General Assembly for each successive period between General Assemblies; the size should be adjusted from time to time so that it is always appropriate to the current level of activity in the field of the Commission. In general, the number of members should be large enough for adequate representation of the field and small enough that the Commission may, in fact, be an effective working body. A recommended number of members in excess of about ten would seem to require some special justification. The Statutes [8.2] provide for the co-option of further members in the period between General Assemblies, but the use of Consultants seems preferable to large-scale co-option. Consultants may be appointed by a Commission as sources of information or counsel, as participants in special projects, or for any other good reason. They add temporary strength to the work of the Commission without making the formal size of the Commission unwieldy. The use of Consultants also provides experience for possible candidates for future membership on a Commission. The President's approval must be obtained before appointing Consultants. (The retiring Chair automatically becomes a Consultant.)

4. The organization of a Commission may be governed by formal Rules of Procedure for any Commission that chooses to formulate such Rules, but there is no rigid pattern recommended for all Commissions. Small Commissions may find it adequate to operate with the Chair as the only officer. Other Commissions may choose a Secretary or other officers as seem appropriate to the programme of each Commission. It is suggested that for Commissions larger than about seven, some form of steering committee composed of the Chair and two other members will be found useful in the preliminary formulation of Commission plans. It is appropriate for some Commissions to divide into sub-Commissions for the performance of separate but related functions.

5. Continuity of experience is essential to the success of all Commissions. Attention should be paid to some scheme of changes in membership which will provide experienced members in every period while observing the limitation of three consecutive full terms for any one member and a fourth consecutive term as Chair [By-Law 7.3]. It is not expected that all persons will automatically serve three successive full terms; ordinarily only one-half to two-thirds of the members will be re-nominated at the end of any term. The Chair in each period should give active consideration to the question of his or her own successor. (The retiring Chair automatically becomes a Consultant.)

6. The foregoing suggestions are provided for the guidance of Commissions and represent the consensus of the Executive Committee, but are not intended as formal requirements of the sort provided by the Statutes and By-Laws or action of the General Assembly. Commissions on publications of the IUCr have special status in some respects as provided in Statutes 7.1, 7.2 and 7.3 and By-Law 7.3.

7. If a member of a Commission wishes to bring anything to the attention of the IUCr he or she should direct the remarks to the General Secretary, in the same way as National Committees, in accordance with Statute 3.9.