Owners and Engineers have turned to the progressing cavity (PC) pump technology for the pumping of sludge at water and wastewater plants because PC pumps can perform well, are relative inexpensive, require low maintenance and there are enough quality products and competition available in the market. At the same time, PC pump manufacturers have tried to push boundaries and expand their offerings into the pumping of higher solids sludges (cake) by improving their design and offering features that reduce overall headlosses. However, there are limitations to what can be pumped by a PC pump since, regardless of the technology, the pumping of sludges containing high concentrations of solids has been a troublesome matter in terms of design and operation for many years. Pumping of high solids sludges can create excessive headlosses in the system leading to excessive wear and tear on equipment or, in certain cases, a complete failure. Understanding and predicting these headlosses for a proper design is often difficult because, at higher solids content, a fluid stops behaving like water. Design guidelines for the pumping of cake with PC pumps are presented and case examples with field data of successful cake pumping installations are reviewed.