Background: The retroperitoneal space contains various organs which can be affected by various non-neoplastic and neoplastic pathological processes. A diagnosis of these retroperitoneal lesions is often difficult. Fine-needle aspiration cytology (FNAC) under image guidance is now becoming an effective tool for the initial evaluation of retroperitoneal lesions. Objective: The present study was undertaken to evaluate the role of ultrasound-guided FNAC in the diagnosis of retroperitoneal lesions in comparison to histopathology and to assess the probable causes of failure in cases of pitfalls in cytodiagnosis. Materials and Methods: During the study period of 5 years, a total of 104 cases of retroperitoneal lesions were aspirated under USG guidance. Seven cases yielded inadequate material, the remaining 97 cases were included in the study group. Results: Out of 97 cases, the kidney was the most common organ aspirated (27 cases; 27.8%). Malignant lesions (68 cases; 70.1%) were much more frequent than benign or non-neoplastic lesions (29 cases; 29.9%). Tuberculosis was the most common non-malignant lesion (14 cases) and renal cell carcinoma was the most frequent malignant lesion encountered (15 cases). In 5 cases (7.9%), the histological diagnosis showed inconsistent results in comparison to cytodiagnosis. Conclusion: USG-guided FNAC is a safe, rapid, relatively cheap and fairly accurate procedure for the assessment of retroperitoneal lesions.