The special requirements of separators used in the manufacture of gelled valve-regulated lead/acid (VRLA) batteries start at the cell-processing steps, where the separator must assist, through its characteristics, the formation of an optimal gel structure. In a gelled VRLA cell, conditions exist that pose additional demands on the separators. In this type of cell, the separator is not a by-stander, but an integral link in the chain of events that comprise the establishment of an efficient oxygen-recombination cycle. In the work reported here, the need for separator materials of very high porosity will be demonstrated, as well as the need for optimal pore-size distributions. An examination is also made of the effect of the surface characteristics of the separator on the formation of gel micro-channels and, in term, the efficiency of the oxygen cycle.