The effective wettability of consolidated sandstone rocks has been determined using the Washburn equation by measuring the rate of imbibition of water, ethanol and their mixtures into cores and thin rectangular sections. The rocks behaved as low energy surfaces with a critical surface energy of spreading, as defined by Zisman, of 28 mN m(-1). This behaviour is believed to be caused by clay particles or organic material present on the pore surfaces. A discussion of the validity and limitations of the Washburn equation for obtaining effective wettabilities in consolidated porous media is presented. The general conclusion is that effective wettability depends on the preparation and general conditions of the samples.