Mathematical models for The calculation of gas holdup in liquid-gas systems from experimental measures of the electrical conductance at several frother levels are presented in this paper. Experimental data were taken by a computer connected to conductance electrodes fixed in art acrylic transparent pilot flotation column. In the first stage of data analysis a relationship between the relative conductance and gas holdup on constant frother concentration was established. In the second stage, variable frother concentration was introduced. Finally, a relationship between the relative conductance, the gas holdup and the interaction between gas holdup and the square root of frother concentration was determined. Alternative models are statistically analyzed. (C) 2001 Elsevier Science Ltd. All rights reserved.