Twenty-two free-ranging North American river otters (Lontra canadensis) from northern and eastern New York were captured and surgically implanted with radiotransmitters as part of a relocation project. The surgical technique involved an incision in the paralumbar fossa and transection through the abdominal musculature to introduce a radiotransmitter into the abdominal cavity. Two complications were encountered. Excessive hemorrhage occurred during one procedure. The otter was treated for blood loss with fluids, and it recovered uneventfully. Surgical incision infection occurred in a second animal. The otter was treated with metronidazole and enrofloxacin, and the wound was cleaned daily with chlorhexidine. The otter recovered uneventfully. Otters were released in western New York state. Postrelease monitoring via radiotelemetry revealed that the otters became established in their new ranges. The intra-abdominal implants did not affect their survival or reproductive potential.