The　endogenous　processes　in　anaerobic　end　and　aerobic　end　sludge　responsible　for　biological　denitrifying　phosphorus　removal　were　compared　during　a　7-d　starvation　under　anaerobic　conditions.　The　results　showed　that　polyphosphate　and　glycogen　were　utilized　simultaneously　to　generate　maintenance　energy　for　both　the　anaerobic　and　aerobic　end　sludge.　During　the　7-d　starvation,　the　decay　rate　of　denitrifying-phosphorus-accumulating-organisms　(DPAOs)　was　higher　for　the　aerobic　end　sludge　than　for　the　anaerobic　end　sludge.　More　energy　was　required　for　maintenance　in　the　aerobic　end　sludge　than　for　the　anaerobic　end　sludge,　with　the　greater　amount　of　phosphorus　release　and　glycogen　degradation　occurring　in　the　aerobic　end　sludge.　Moreover,　different　metabolic　pathways　for　the　endogenous　processes　were　observed　for　the　anaerobic　and　aerobic　end　sludge.　After　the　7-d　starvation,　the　activity　of　DPAOs　decreased　more　for　the　aerobic　end　sludge　than　that　for　the　anaerobic　end　sludge.　(C)　2011　Elsevier　Ltd.　All　rights　reserved.