Oviduct fluid was collected from 24 mature female rabbits in estrus fitted with a copper intrauterine device (IUD) in one of the uterine horns by laparotomy and examined for total sugar and protein content. The percentage of total sugar in the dry protein-containing material from the experimental side was 7.3 compared to 5.2 from the control side. The percentage of total protein was 67.0% of the total dry material from the experimental side, compared to 77.7% in the control side. Cellulose acetate electrophoresis confirmed these findings, demonstrating an increase in the strength of the periodic acid-Schiff stain bands of the glycoproteins from the copper IUD side and a weaker Ponceau-S stain of the protein bands. The ampullary-isthmic area and the uterotubal junction of both oviducts were examined with the scanning electron microscope. The secretory and ciliary cells on the copper IUD side were damaged in these two areas. These changes can be attributed to the presence and action of the copper ions in the oviduct milieu.