Background: High-grade evidence for recommendations about the appropriate lag-time from implantation to utilization of the catheter regarding urgent PD is lacking. The objective of this study was to compare immediate and delayed utilization of the Tenckhoff catheter in urgent PD. Methods: 160 patients beginning urgent automated peritoneal dialysis (APD) were randomized into two groups of 80 patients each. In the immediate utilization group (I), the catheter was used immediately after the surgical implantation; in the delayed utilization group (D), the catheter began to be used 3-5 days after the surgical implantation. The catheter function and complications in the two groups were compared after a one-year follow-up. Results: Patients in I and D were aged 42.5±18.5 and 49.2±19.6 years and their BMI was 25±2.5 and 25±3 kg/m2, respectively. The lag-time from implantation to utilization of the catheter was shorter in I (4±2 h) than in D (79.5±35.7 h; p < 0.01). Both groups had similar frequency of overall complications: 10 patients (12.5%) in I and 12 patients (15%) in D developed catheter related complications within 12 months. Group I complications were leakage (2), migration (2), and peritonitis (2); group D complications were leakage (3), migration (4), and peritonitis (2). Actuarial survival of the catheter showed no differences between the two groups at one year. Conclusions: Immediate utilization of a surgically implanted Tenckhoff catheter is feasible and safe, since it is not associated with an increased frequency of complications.