Chloroform removal by activated carbon with a view to elucidating the dominant factor was investigated for the assurance of safe water. A significant correlation was recognized between the amount of chloroform adsorbed and the amount of water adsorbed as the indicator of surface hydrophobicity of adsorbent. No significant correlations were recognized between the amount of chloroform adsorbed and the surface area, pore volume or surface pH. It was concluded that a dominant factor of chloroform adsorption by activated carbon was the degree of surface hydrophobicity of adsorbent.