The refrigerants with high global warming potential (GWP) will be phased out, which has stimulated research to find replacement fluids. The chemical and thermophysical properties of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) have made them the promising candidate. Accurate thermophysical properties will be essential to design and develop efficient processes that use these compounds. In this work, the viscosity of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) in the temperature of (243 to 363) K from saturated pressures up to 30 MPa was reported. With regard to R1234ze(E), measurements were performed at temperatures between (243 and 373) K from saturated pressures up to 30 MPa. The viscosity was measured using a vibrating-wire viscometer with a combined expanded uncertainty of about 2.0%. The scheme based on a hard-sphere model was used to correlate the experimental results. (C) 2013 Elsevier Ltd. All rights reserved.