The influence of organic additives such as benzoic acid, iso-amyl alcohol and propanol on hydrodynamic characteristics of an internal loop airlift reactor was investigated. The effects of the draft tube to column diameter ratio, D-E/D, and superficial gas velocity, U-sg on the gas holdup in various sections of the reactor (riser, downcomer, overall) and liquid circulation velocity were reported. The gas holdup and the superficial liquid velocity in the riser and downcomer increased with an increase in the superficial gas velocity, U.,. In the present investigation, the D-E/D ratio varied from 0.34 to 0.76 and the overall gas holdup and downcomer gas holdup increased with an increase in the D-E/D ratio and the optimum was found to be 0.49. The riser gas holdup decreased with an increase in the D,,ID ratio. The maximum volumetric liquid circulation rate was obtained with a D-E/D ratio of 0.49 to 0.59. The addition of additives influenced the bubble coalescence reduction and increased the gas holdup. The addition of iso-amyl alcohol resulted in the maximum gas holdup. The superficial liquid velocity in the riser and downcomer decreased with the addition of additives. Correlations for the prediction of gas holdups in the different sections of the reactor and liquid circulation velocity were proposed.