After more than a decade of basic research with the help of cavimetry, retentiometry, X-ray and ultrasonography, a new intrauterine contraceptive device, the CU SAFE IUD, was developed. The plastic body of the device shows the following properties: uterine cavity compatible, enhanced flexibility, low surface area, fundus-seeking anti-expulsive design, no anchoring mechanisms, and one monofilament without a knot embedded into the shaft. The copper surface area of 300 mm2 guarantees a high efficacy for up to five years. The CU SAFE 300 IUD fulfils all requirements of the International Organization for Standardization (ISO) in regard to intrauterine devices. This paper reports on the first-year results of a large ongoing CU SAFE 300 study, number of insertions 1150. 1017 acceptors of all fertile age groups accumulated 10,576 woman-months of use. The event rates were as following: pregnancy 0.6; expulsion 0.6; removal for bleeding 4.2, for pain 1.5; infection 0.0; other medical 0.9; non-medical 3.1. The continuation rate was 89.1 at the end of the first year. The increased safety and high efficacy of the CU SAFE 300 provides comfort for both user and partner. The ease of insertion without a plunger and gloves (inserter tube diameter 3 mm) and the ease of removal (force of traction approximately 1 N) mean safety also for the medical and paramedical fitter of the CU SAFE 300 IUD.