An improved recording rotational high shear viscometer has been developed. The instrument employs concentric steel cylinders with unusually narrow and precisely defined shear clearances. Both shear rate and stress are continuously and independently recorded. Improved cylinders and other additional features have led to accurate viscosity measurements at shear rates from 5×102to 2×106sec−1. The temperature range is −20 to +150°C with a viscosity range which varies inversely with the desired shear rate for measurement. The shear rate range and the upper limit, 2×106sec−1, exceed all previous reports of measurement at defined conditions in a homogeneous, isothermal shear field.