Three personal cases are presented to indicate the growing need for thrombectomy as a method of treatment of renal-vein thrombosis. In addition to known causes of renal-vein thrombosis (e.g. iatrogenic, post-traumatic) there is the so-called spontaneous renal-vein thrombosis especially in newborns. The possibility of renal-vein thrombosis must be considered in the presence of sudden, circumscribed pain in the flanks, haematuria and albuminuria, large kidney shadow radiologically, loss of renal function. Reported cases and the three personal ones suggest a trial of thrombectomy. It is not known how long the kidneys can tolerate venous occlusion. But the personal observations suggest that even occlusion lasting for serveral days may be reversible. In one patient with renal-vein thrombosis after unrecognised misplacement of a Mobin-Uddin filter into the right renal vein, surgical restoration of venous drainage after several weeks indicates that long-term observations are necessary to judge final results.