Information on dewatering properties of municipal wastewater sludges is scant and poorly organized. A Task Force has collected information on wastewater sludges with particular emphasis on sludges produced when lime, Fe(+++) or Al(+++) are added for the purpose of P removal to some portion of the wastewater treatment sequence. Data are presented on the thickening and dewatering characteristics of the sludges. Most of the information relates to the mass of sludge produced and its filtering properties. Sludges produced when lime is added to wastewater have greater solids content after settling and dewater at greater mass rates than conventional sludges. However, mass of sludge per volume of wastewater is greatly increased. Considerable information is available on such sludges. Sludges produced when Al(+++) or Fe(+++) is added to wastewater dewater more poorly than conventional sludges and sludge solids content is less. Sludge mass is greater than in conventional treatment but not as great as would be produced by lime addition. Information is clearly not yet adequate for accurately predicting dewatering properties of such sludges.