We studied the copper-releasing ability, weight and microscopic appearance of 2 copper-bearing intrauterine devices (IUDs), Copper-T Cu 200 (CuT) and Nova-T Cu 200 Ag (NovaT), after they had been in utero for up to 8 years. In addition, we studied whether IUDs removed from pregnant women showed different copper release. We found that IUD weight was a linear, negative function of duration of use, and that less than 20% of total copper would be released over a period of 8 years. The average copper-releasing ability was significantly higher for CuT than for NovaT (82.6 ± 6.4 vs. 42.7 ± 2.6 μg/day). The copper release was constant and thus unrelated to duration of use. Copper-releasing ability was similar in IUDs removed from pregnant and non-pregnant women. Fragmentation or minor defects only occurred in 3% of the IUDs and no correlation was found between deposits or corrosion and copper release rates. We conclude that CuT and NovaT both have constant copper release for at least 5-6 years and that the useful life-span probably can be prolonged to 6-8 years or more.