OBJECTIVE : To determine the degree of agreement between arterial and venous blood gases in anesthetized lambs using a point-of-care analyzer. METHODS : Prospective experimental study. METHODS : A group of 12 female Dorset cross-bred lambs, weighing 37.3 ± 7.4 kg (mean ± standard deviation). METHODS : Lambs were anesthetized with isoflurane for catheterization of the jugular vein and femoral artery, and blood samples were collected simultaneously for analysis of pH, PCO2, PO2, base excess (BE), bicarbonate ( [Formula: see text] ), total carbon dioxide (tCO2), oxygen saturation (SO2), ionized calcium (iCa) and potassium (K+) using the Vet Scan i-STAT handheld analyzer. The Bland-Altman method was used to calculate agreement between arterial and venous measurements. RESULTS : Strong agreement was identified between arterial and venous pH (bias = 0.04; 95% limits of agreement = 0.02-0.06), K+ (bias = -0.1 and 95% limits of agreement = -0.8 to 0.5) and iCa (bias = 0.04; 95% limits of agreement = -0.08 to 0.0003). There was poor agreement for PO2 (bias = 168.0; 95% limits of agreement = 77.4-258.7) and SO2 (bias = 9.1; 95% limits of agreement = 2.8-15.3), as these values were higher in arterial blood than in venous blood. Moderate agreement was present for BE (bias = 1.7; 95% limits of agreement = -2.7 to 6.1), PCO2 (bias = -2.1; 95% limits of agreement = -7.5 to 3.4), [Formula: see text] (bias = 1.1; 95% limits of agreement = -3.1 to 5.3) and tCO2 (bias = 1.0; 95% limits of agreement = -3.3 to 5.3). CONCLUSIONS : Venous blood can be used for the measurement of pH, K+ and iCa in anesthetized Dorset cross-bred lambs. Arterial blood is required for accurate measurement of PO2, SO2, PCO2, [Formula: see text] , tCO2 and BE to assess systemic blood oxygenation and pulmonary function in anesthetized Dorset cross-bred lambs.