Data is presented on the use of the Merchant's Copper Coil (MCC) IUD by 400 private patients between March 1981-June 1985. The MCC is a polyethylene IUD in the shape of an open ring largely enveloped in a copper thread .2 mm in diameter and with a surface area of 251 sq mm. Overlapping of the extremities of the MCC allows it to adapt to uterine activity and to all types of uterus. Danger of perforation during a vigorous uterine contraction is minimized by the absence of protruding extremities. Insertion is done using a tube of 3.6 mm in diameter, making the procedure easy and painless even in nulliparas. The MCC is available in different sizes. The size selected in the series was not significantly related to the age of the woman but was slightly related to parity. The average age of users was 26.5 years and the average parity was 1.4. All insertions were done in the office without anesthesia except in 1 nullipara who needed a local cervical anesthetic. 46.7% of users were 20-25 years old, 31.3% were 26-30, and 16% were 31-35. 10.7% were nulliparas, 50.3% had 1 child, 31.5% had 2 children, 5.5% had 3, and 2.0% had 4 or more. 83.5% had secondary educations or better. 80.5% had interval insertions and 19.5% had insertions 2-4 weeks after 1st trimester abortions. Insertions were without complications except for spotting or bleeding in 9 cases lasting from a few hours to 3 days. Between March 1981-June 1985, 118 women used the MCC for 2 years and the total number of woman months of use was 6864. In the 2nd year of use, the cumulative net rates using the Tietze method and numbers of events respectively were .3 and 1 for pregnancy, 4.1 and 14 for expulsion, .6 and 2 for removal because of bleeding, 0 and 0 for removal because of pain, 5.0 and 12 for removal because of other medical reasons or to change the IUD, 13.4 and 34 for desired pregnancy, and 2.3 and 6 for personal reasons. The continuation rate was 91.5% after 1 year and 74.3% after 2 years. There were no cases of perforation due to the IUD. The crude rates of termination per 100 users after 1 and 2 years respectively were 0 and .4 for pregnancy, 3.3 and 4.5 for expulsion, .6 and .6 for bleeding or pain, 1.1 and 5.8 for other medical reason, 3.7 and 15.4 to become pregnant, and 1.0 and 2.5 for other personal reason.