Abstract: A fractionator for fractioning a suspension in at least two fractions, including a drum rotatable about a substantially horizontal access and having axially spaced end walls, a centrally arranged inlet for suspension, a flow channel for suspension in the drum, and outlets for fractions. The flow channel extends from the inlet back and forth between the end walls of the drum and radially outwards towards an outlet for the at least two fractions. Preferably the flow channel is defined by substantially concentric cylindrical walls of which every second wall is alternatively tightly connected to one or the other of the two end walls. The fractionator is useful in a continuous fractioning process.