In recent years a number of designers seem to have eliminated rectangular clarifiers form their design repertoires. Many others never have designed one. This appears to be particularly true for clarifies following activated sludge aeration basins. Some states have even taken, or are considering, positions favoring circular clarifiers over rectangular clarifiers. In my view, it is a mistake to overlook rectangular clarifiers. In my firm’s practice, we find both circular and rectangular clarifiers have their place. We’ve designed about the same number of each. Since it is understood that Dr. Parker will address circular clarifiers, my remarks will concentrate on rectangular clarifiers¾specifically rectangular clarifiers following activated sludge aeration basins.