Interfacial areas were determined for gas‐liquid systems in a column with transparent walls by the chemical and two physical methods: photography and light attenuation. The advantages of the different methods are discussed and improvements in the physical methods are described. By using a Data Tablet Digitizer, the photographic technique provides additional information on the gas dispersion without increasing the amount of work needed for analysis of the photographs. Use of the light attenuation technique is extended to conditions when multiple scattering and stray light must be taken into account; it can then be used up to values of optical path densities equal to 80.