Response surface methodology was used to investigate the potential of unhydrogenated palm oil (PO), with and without peanut shell flour (PSF), to prevent oil separation in peanut butter. Percent oil separation, texture and color attributes were measured after 0, 1 and 2 wk storage at 15, 25 and 35 degrees C. Computer-generated contour plots indicated that 2.0-2.5% PO should effectively stabilize peanut butter stored at 21-24 degrees C for greater than or equal to 1 year without affecting color. PSF (greater than or equal to 0.8%) decreased L value of color by greater than or equal to 5% but did not increase firmness of experimental products containing PO. Samples stabilized with PO were softer than those containing a commercial stabilizer.