This work investigated drag reduction in turbulent flow of water using air bubbles and other additives. The first phase of the experimental program dealt with the effects of small air bubbles on wall shear stress and friction factor. The friction factor versus Reynolds number data exhibited different trends at low and high Reynolds numbers. At high Reynolds number, the two-phase mixture behaved as a pseudo-homogeneous system and the friction factor followed the single-phase behaviour. At low Reynolds number, the observed friction factor was significantly higher than that of single-phase fluids. The observed trends were interpreted in terms of the average bubble sizes predicted from a well-known empirical equation. The second phase of the experimental program investigated the effects of additive/air-bubble combinations on drag reduction in water flow where the additives used were frother and polymer. The addition of frother made the flow more homogeneous and the mixture followed the single-phase behaviour more closely. In the absence of polymer, the injection of air bubbles generally increased the wall shear stress and friction factor compared to single-phase flow, especially at low Reynolds number. However, the addition of polymer to two-phase water/bubbles mixture induced drag reduction up to as high as 60%. The friction factor data for polymer-solution/bubbles combination followed the polymer-solution line, regardless of the presence of frother.