Laboratory digestion studies were carried out in order to better understand the effect of digestion on conditioning and dewatering of waste activated sludges. Changes in biopolymer content, dewatering rate as measured by both capillary suction time (CST) and specific resistance to filtration (SRF), and conditioning requirements were measured. It was found that when waste activated sludge (WAS) was anaerobically digested, substantial quantities of protein were released into solution, increasing conditioning chemical requirements and the specific resistance to filtration (SRF). For aerobically digested sludges, both proteins and polysaccharides were released and together, they accounted for the increased conditioning demand and SRF. For both anaerobically and aerobically digested sludges, the degree of deterioration in dewatering and conditioning requirements were related to the degree of volatile solids (VS) destruction.