Drainage and coalescence within a vertical foam fractionation column were measured experimentally. This was accomplished by constructing and operating a vertical column equipped with a series of electrical conductivity cells mounted internally at various levels. With these cells, the variation in the local foam density along the column was determined from the variation in the local conductance. The change in bubble size was measured photographically. Other variables were determined by conventional means. The surfactants employed included Triton X-100, albumin, and saponin. Reflux ratios ranged from zero to infinity. Consideration was given to the increased separation attainable by vertically elongating the liquid pool so as to establish a concentration gradient within it. A detailed analysis of this phenomenon was prepared in terms of potential flow and penetration theory at the upstream portion of the bubble, plus a renewing wake downstream and an overall solute balance.