Ureteral peristalsis and pelvic pressure were studied in the patients with kidney stones, which were treated by means of percutaneous nephrolithotripsy (PCNL). Besides the common urological investigations the peristalsis status of the upper, middle and lower thirds of the ureter was evaluated with the use of the multichannel impedance uretrography in 12 patients immediately before the PCNL. Measurements of the pelvic pressure were performed in 18 patients 2-3 days after the stone removal and placement of the nephrostomy tube. Ureteral peristalsis in patients with kidney stones was characterized via strong contractions (amplitude 1.61±0.16 and 1.78±0.21 Om) of the upper and middle cireter parts, with the retrograde direction of the peristalsis (antiperistalsis) in 60% of the patients, and predominately (78%) simultaneous (cystoid) contraction waves in the lower third of the ureter. At that, the tonus of the ureteral wall in the lower third was higher (8.06±0.69 units), than in upper and middle thirds of the ureter (3.66±0.37 and 3.53±0.48 units). In the early postoperative period after PCNL (Day 1) high pressure in the pelvis was registered in all patients (20.1±0.7, range 11.6-31.3 cm H20) with the mean urine output from the nephrostomy drainage of 0.80± 0.03 l/day. Correlation analysis of the peristalsis status and intrapelvic pressure showed a positive correlation of the pressure with the contraction amplitude of the upper ureteral third: contractions were more prominent by 45, 32 and 95% in patients (n=12) with higher intrapelvic pressure (23.8±0.8 cm H20) in comparison with the patients (n=6), the intrapelvic pressure of which was 12.8±0.6 cm H20. Active and disorganized ureteral peristalsis in this group of patients is probably a reaction to the neuro-humoral irritation from the kidney stones. At that, a high intrapelvical pressure could be not a consequence of the operational trauma and reaction to the endoscopic operation only, but also a result of the prominent retrograde contractions of the proximal ureter.