Seven lymphocoeles have complicated 158 cadaver and 18 related live donor transplants performed over six years. The purpose of this study is to review the clinical, diagnostic and therapeutic problems encountered with lymphocoeles at this centre. Presentation was insidious, delayed (50 days post-op), and manifested by one or more of the following: palpable rectal or supra-pubic mass; unilateral leg oedema; recurrent urine infections with radiographic evidence of obstruction; filling defect in bladder on routine IVP. Possible pathogenetic factors: transplants performed on side of functioning Scribner shunts (6/7 cases); severe rejection episodes with graft lymphatic leak (1/7 cases). Differentiation from urinomas, haematomas, perinephric abscesses or other causes of obstructive uropathy were facilitated by: needle aspiration; IVP and cystogram, serial ultrasound sonography. Lymphangiography was not used. Treatment was conservative in three, repeated aspirations were performed in two and formal drainage procedures were required in three patients. Repeated cyst aspirations resulted in serious infections in both patients. Marsupialisation into the peritoneal cavity failed in one. CONCLUSIONS 1) The graft should be anastomosed on side opposite a functioning shunt. 2) Lymphocoeles have an occult presentation and should be actively sought for as they may produce urinary obstruction. 3) Serial ultrasound is an excellent method of diagnosis and follow-up. 4) Unless urinary obstruction is present management should be conservative as spontaneous resolution may occur. 5) Ideal surgical management is problematical. Repeated needle aspirations should be approached with caution. Lymphocoeles are an uncommon but well documented complication of renal transplantation (Schweizer et al, 1972; Koehler et al, 1972; Christiansen et al, 1974; Rashid et al, 1974). They represent definite hazards and can either directly or indirectly contribute to morbidity or even mortality in the post-transplant patient. They must be differentiated from other pelvic masses such as urinomas, haematomas and perinephric abscesses as they all require different modes of treatment. As a rule, the diagnosis of one from another is straightforward, but as certain clinical features are shared, differentiation can on occasions be more difficult. In order to clarify some of these problems and outline a mode of therapy, a study was carried out in patients who have presented with lymphocoeles in our unit.