The authors have analysed the 220 native, erect and supine abdominal X-ray views of 65 males and 45 females with the acute pancreatitis. The localized spontaneous pneumoretroperitoneum inside the left posterior pararenal space was observed in 3.8% of patients (4 cases). The extraperitoneal gas paralleled laterally and inferiorly the margins of kidney and medially the lateral margin of the iliopsoas muscle. Superiorly the gas collection overlay the suprarenal area and outlined the medial crus of the diaphragm, occasionally. The plain-film roentgenogram depended on the quantity of the extraperitoneal gas and of the perirenal fat, besides the subdiaphragmatic adhesions. The pathognostic pneumoretroperitoneum evolved within the initial stage of acute pancreatitis. Afterwards the extraperitoneal gas was hidden by the intraluminal gas bubbles and fluid levels of the dilated small and large bowels.