employed using donor sperm, surplus embryos may be donated to other women or couples and used in embryo transfer procedures. When donor sperm is used for IVF treatments, there is a risk that large numbers of children will be born from a single donor since a single ejaculate may produce up to 20 straws for IVF use. A single straw can fertilise a number of eggs and these can have a 40% to 50% pregnancy rate. 'Spare' embryos from donor treatments are frequently donated to other women or couples. Many sperm banks therefore limit the amount of semen from each donor which is prepared for IVF use, or they may restrict the period of time for which such a donor donates his sperm to perhaps as little as three months (about nine or ten ejaculates). Choosing donors Information about donor In the US, sperm banks maintain lists or catalogues of donors which provide basic information such as racial origin, skin color, height, weight, color of eyes, and blood group. Some of these catalogues are available via the Internet, while others are only made available to patients when they apply for treatment. Some sperm banks make additional information about each donor available for an additional fee, and others make additional basic information known to children produced from donors when those children reach the age of eighteen. Some clinics offer "exclusive donors" whose sperm is only used to produce pregnancies for one recipient female. How accurate this is, or can be, is not known, and neither is it known whether the information produced by sperm banks, or by the donors themselves, is true. Many sperm banks will, however, carry out checks to verify the information requested, such as checking the identity of the donor and contacting his own doctor to verify medical details. Simply because such information is not verifiable does not imply that it is in any way inaccurate, and a sperm bank will rely upon its reputation which, in turn, will be based upon its success rate and upon the accuracy of the information about its donors which it makes available. In the UK, most donors are anonymous at the point of donation and recipients can only see non-identifying information about their donor (height, weight, ethnicity, etc.). Donors need to provide identifying information to the clinic and clinics will usually ask the donor's GP to confirm any medical details they