Abstract: A viscometer comprising a first member having an internal surface which is at least part-cylindrical, a second member which is cylindrical and is eccentrically mounted relative to the said internal surface, the first and second members defining therebetween a gap for receiving liquid to be tested, a drive means for causing relative rotation between the first and second members and pressure detecting means for detecting a pressure difference between liquid in a region of the said gap and liquid in a second region. The invention also provides a method of measuring viscosity.