Intrathecal drug administration via implanted pump is an effective treatment for intractable pain and spasticity but can be compromised by catheter-related complications. To determine the etiology of catheter-related complications, we have conducted a multicenter, prospective study of the long-term performance of a one-piece catheter system. Data pertaining to catheter-related complications were collected at implant and at specified times during the follow-up period. Catheter implantation characteristics that might affect complications were assessed. Two hundred nine patients were studied at 22 participating centers, with 1764 cumulative patient-months of catheter experience. Forty-nine catheter system complications occurred in 37 patients (7 complications related to the catheter itself, and 42 complications related to the implantation procedure). The 9-month complication-free "survival" rate was 78.9% overall (95.5% for the catheter itself). No specific catheter implantation characteristics were associated with the occurrence of complications. These data indicate that the incidence of complications for a one-piece catheter system is similar to that of commercially available two-piece systems, and highlight the need for careful surgical technique during implantation.