Delafossite-type solid solution, CuFe1-x Al (x) O-2, was synthesized and its oxygen storage capacity (OSC) was investigated under oxidation/reduction cycle using a pulse injection method. CuFe1-x Al (x) O-2 was synthesized by heating at 1100-1150 A degrees C in N-2 flow. OSC values for x = 0.1 and 0.3 were larger than that for x = 0 above 500 A degrees C, indicating that substitution of Fe3+ by Al3+ improved OSC. For x = 0.5-1.0, temperature at which OSC increased steeply shifted upward. Results of X-ray diffraction (XRD) after the thermogravimetry and differential thermal analysis (TG-DTA) measurement in air for CuFe1-x Al (x) O-2 (x = 0-0.7) indicated that oxidative decomposition of delafossite phases to CuO and spinel-type phase occurred. In addition, Cu reduction temperature estimated by the temperature programmed reduction using H-2 (H-2-TPR) shifted to higher temperature with increasing Al content. The XRD results of the samples after H-2 and O-2/He pulse injection suggested that the oxygen storage/release behavior was caused by reversible oxidation/reduction process between CuFe1-x Al (x) O-2 delafossite and (Fe1-x Al (x) )(3)O-4 spinel phase +Cu.