Therapy (case series). 4. To present our experience of retroperitoneoscopic partial adrenalectomy (RPA) for small adrenal tumours, as with modern imaging methods small adrenal lesions are being diagnosed more commonly, and retroperitoneoscopic adrenal surgery for small adrenal tumours (< or =1 cm) can be challenging. We retrospectively reviewed the records of 389 consecutive retroperitoneoscopic adrenalectomies from September 2005 to December 2008, 88 of which were small adrenal tumours and treated by RPA. Ultrasonography and computed tomography (CT) were used in all patients before RPA, and magnetic resonance imaging or positron emission tomography/CT in some patients. We used RPA for adrenal tumours and total adrenalectomy for adrenal cancer. During the surgery, the internal part of the adrenal gland close to the retroperitoneum was freed first, and the whole adrenal tissue was dissected completely. The preoperative imaging was important in these procedures. There were no deaths; conversions to open surgery were necessary in four patients (4.5%), the reasons being a missing target in two, massive haemorrhage caused by central adrenal vein injury in one, and severe adhesion in one. The mean (range) size of the adrenal tumours was 0.7 (0.5-1.0) cm, including 69 aldosterone-producing adenomas, 11 nonfunctional adrenal adenomas, three Cushing syndrome, two phaeochromocytomas, two myelolipomas and one melanoma. The operative duration in the initial 38 cases was significantly longer than that in the subsequent 50 (P < 0.01). However, there was no significant correlation between estimated blood loss and the number of procedures. Tumour size did not correlate with estimated blood loss and operative duration. There was no significant correlation between body mass index and operative duration. RPA is a safe, effective and minimally invasive therapeutic option for patients with small adrenal tumours. With improved operative technique the RPA has been completed in more quickly. Freeing the internal part of the adrenal gland close to the retroperitoneum first, and exploring the whole adrenal tissue during surgery are the key points of RPA. The location of the small adrenal tumour can be different from that shown on imaging before surgery, and the abnormality of the adrenal gland should be considered.