PIP: Total copper concentrations in the cervical mucus of 90 IUD-free women were measured at different times in their menstrual cycle using an atomic spectrophotometer and a 'Perkin Elmer 303' graphite furnace. The same procedure was done in another 109 subjects using various types of IUD (9 Dalkon Shields; 4 Progestaserts; 8 Copper Ts; 10 Copper Ts; 5 ml Cu 250s; 73 No-Gravid 1s, and; 4 No-Gravid 2s). Another groups of 123 IUD users was studied (16 Copper Ts; 16 Gravigards; 60 No. Gravid 1s; and 31 No-Gravid 2s), as were 17 IUD-free women and 30 No-Gravid IUD users. The cervical mucus samples were subjected to some spermetozoa tests (drop-to-drop admixture and penetration test and Kremer Test). The copper values in all subjects were lower in the follicular than in the luteal phase of the menstrual cycle. Women with copper IUDs also exhibited higher copper levels than those with non-copper IUDs. Copper levels were highest (up to 3 times) with the No-Gravid devices, even when measured after 30 months from insertions. Daily copper losses were also found to be greatest with the No-Gravid devices, with the greatest losses occurring within the 1st 6 months. Estimated time for 50% loss was 4 years. In comparing interaction of spermatozoa with the cervical mucus of women with No-Gravid devices and those without IUD, lower migration distances and penetration densities were observed in the No-Gravid cases.