This single-blind case–control study compared the complications of 2 intrauterine devices in consecutive referrals for device insertion in clinics of Shaheed Beheshti University of Medical Sciences, Islamic Republic of Iran. Women who met the inclusion criteria (n = 110) were randomly allocated to receive copper T380A (controls) or Cu-Safe 300 (cases). Moderate or severe pain during the device insertion was reported in 69.1% of controls and 47.3% of cases. Bleeding, vertigo and crampy pain at insertion were not significantly different between the groups. After 3 months follow-up, blood spotting was reported in 16.3% and 32.7% of controls and cases respectively. The Cu-Safe-300 group had less pain and menstrual bleeding but copper T380A had less spotting after 3 months. Studies on longer term complications are strongly recommended.