The surface of 25 copper IUCDs and 25 inert IUCDs that had been in utero for less than 6 months or more than a year was examined by the scanning electron microscope and the deposits were extracted from another 100 copper and inert IUCDs that had been in utero for less than 6 months or more than a year and examined by the atomic analyser. The most apparent changes were, respectively, amorphous deposits and cellular debris, crystalline deposits, cracks, duplex coating, distortion and corrosion. Duplex coating was found only on inert IUCDs, but corrosion was found on copper IUCDs. The duration of use of the IUCDs had marked effect on the type of the deposits. Bleeding with IUCDs was associated with a thick layer of amorphous deposits. The contraceptive effect of the IUCDs was found to depend on the reaction of the host to the applied IUCDs rather than the type of device. The surface deposits were found to contain mainly calcium, phosphorus and magnesium.