Samples of three commercial varieties of cassava starch (Manihot utilissima Pohl) have been prepared in laboratory in order to find out it they differed in relation to viscosity. These varieties were Branca de Santa Catarina, Brava de Itu and Cafelha, considered to be very promising in relation to root yield. Viscosity measurements were made in Brabender Amylograph Viseograph and the data obtained were submited to statistical analysis. The results indicated that these cassava varieties differ substaneially in their starch viscosity.