We report a new operative technique for plastic correction of uretero-pelvic junction (UPJ) obstruction: dismembered spiral flap pyeloplasty. It is similar to the method described by Culp & DeWeerd in that a flap is made spirally but different in that UPJ is detached. Relatively a long and wide spiral (oblique) flap, the apex of which directs cranioventrally or craniodorsally, is made using the dilated pelvis. The apex of the flap is reflected downward and anastomosed to the split ureteral end. Because the flap is made obliquely, one side of the flap base is approximated to the opposite pelvic margin; this helps to make gradual funnelling of pelvio-ureteric transition. The method seems to be fit for cases with considerably long stenosis of UPJ and with the UPJ locating relatively close to the medial margin of the renal parenchyma. Seven of 26 pyeloplasties were done by this method in our institute, and all the 7 cases had satisfactory results.