The axial velocity profile (local velocity versus time or position) of single bubbles in the presence and absence of frother (Dowfroth 250, MIBC and pine oil) was measured in a water column over a distance of 4 m. Temperature along the column was maintained uniform and constant at 30 degrees C by a temperature-controlled water jacket. Single bubble sizes 0.9, 1.5, 2.2 and 2.7 mm in diameter, covering a range of interest in flotation, were studied. A bubble generation frequency was selected such that velocity was independent of frequency. To follow the bubble during its rise, a video camera supported on a track and capable of moving vertically at adjustable speeds was employed. In the absence of frother, the profiles showed two stages: first the velocity increased rapidly and then decreased continuously over the 4 m. In the presence of frother, a third stage was reached, a constant (terminal) velocity. The terminal velocity was not dependent on frother concentration but, was a function of frother type. The shape and motion (path) of the bubble were also recorded. The observations are qualitatively explained in terms of time-dependent adsorption of surfactants, either present as contaminants in tap and distilled water or deliberately added in the case of frother.