A vertical uniaxial extension apparatus was developed for determining elongational properties of Mozzarella cheese over the course of one month of refrigerated storage. Cheese specimens suspended in hot oil (60C) first underwent melting and then stretching under the influence of a constant force. Samples did not break even after 400% extension. Strain rate and sample temperature both increased during a test. Transient elongational (TE) viscosity of Mozzarella cheese decreased with increasing strain rate and sample temperature. Proteolysis of caseins in Mozzarella, determined by gel electrophoresis, did not alter its TE viscosity to an extent measurable by our method.