30 women (24-34 years; parity 3-6) randomly selected from the family planning clinic at Al-Azhar University Hospital, Cairo, were divided into 3 groups: 1) 10 normal fertile; 2) 10 women fitted with T-Cu-200 for 2-20 months; and 3) 10 women fitted with Lippes loop for 2-8 years. On the 13th-15th day of the cycle cervical mucus was sample and tested for sperm penetration, motility, turbidity, Spinnbarkeit, and ferning. Sperm penetration tests used the sperm migration meter of Kremer and turbidity and clarity were assessed by the naked eye. Sperm penetration and motility were greatly impaired with Cu-device users, while with Lippes loop the findings approached that of the normal control women. Turbidity results were significant (p less than .01) for Cu-device users. Diminished Spinnbarkeit and positive ferning were also observed in the presence of the Cu device. The impaired sperm penetration and immobilization with the use of the Cu-devices as opposed to Lippes loop suggests a local lethal effect of the increased copper on cervical mucus rather than a local foreign body reaction.