Diagnosis of M. paratuberculosis infections in cattle by detection of serum antibodies using a commercial absorbed ELISA kit from IDEXX Laboratories, Inc. has been offered by our laboratory as a service since January, 1991. The first year the service was offered, 429 submissions (accessions) constituting 9,812 sera were tested. Each year the number of accessions and sera has increased. In 1995, 3,337 accessions constituting 22,193 cattle sera were tested. In 1995, approximately 65% of samples were from Wisconsin cattle; the remainder were from cattle in neighboring states. Sample submissions have had a seasonal pattern with a greater number of submissions occurring in the fall and spring. Two-thirds of the submissions (accessions) were single samples. Of these, roughly 50% were ELISA-positive for M. paratuberculosis antibodies. For accessions with > 50 sera submitted, generally whole herds, 5.90% and 4.95% tested ELISA-positive in 1994 and 1995, respectively. Overall, for past 5 years, while the number of samples submitted has steadily increased, the percentage of positive sera has remained relatively constant at 10%±2%. Clients report that ELISA results correlate well with clinical findings and that the ELISA is a useful tool in a control program for bovine paratuberculosis.