CT-guided core biopsy for retroperitoneal lesions. Experience in 136 procedures Background: CT-guided core biopsy is a widely used diagnostic technique for retroperitoneal lesions. Aim: To evaluate the diagnostic yield and safety of this procedure. Material and Methods: Review of medical records of 136 patients aged 57 ± 16 years (55% males) subjected to core biopsies performed between 2006 and 2016. Procedure images, biopsy reports and patients' medical charts were reviewed. Diagnostic yield was calculated in those patients whose final diagnosis was confirmed using strict criteria for malignancy. Results: A final diagnosis was confirmed in 122/136 patients. Of these, 110 had malignant lesions. The sensitivity and global accuracy of the procedure for malignancy were 93%. In only 4 of 13 benign lesions (31%), a specific diagnosis was obtained with the biopsy. Only minor complications were reported (6 small, self-contained hematomas). There were no major complications. Conclusions: CT-guided core biopsy of retroperitoneal lesions is a safe procedure, with an excellent diagnostic yield.