The development of the Copper 1 IUD (Cu 1) was an attempt to decrease the incidence of unpleasant side effects (primarily pain and bleeding) associated with IUD use, by reducing the size of the vector carrying the copper. The Cu 1 consists of a straight stem with crossarms in an "X" configuration, designed to anchor the IUD in place. The device was tested in 98 interval women in the Hospital Barros Luco in Santiago, Chile who were asked to return at 1, 3, 6, and 12 months post-insertion for follow-up examinations. There was only 1 removal for bleeding and pain; however, both pregnancy and expulsion rates were high at 9.0 and 16.0 respectively after 12 months. The crossarms did not keep the device in place as expected. The high pregnancy rate may have been due to the reduced size of the IUD and to increased displacement/expulsion. Future efforts to decrease IUD size will be dependent on designing an IUD which will be less easily expelled or displaced.