Previous work has focused on the use of microscopy to explore the mechanisms of deformation in polymer nanocomposites. That technique creates a qualitative representation that may not be statistically representative of the bulk properties. This paper illustrates the utility of solid-state NMR, which inherently measures bulk behavior, to both identify and quantify mechanisms of deformation. Specifically, in this study, increases in the interfacial area of various modifications of Cloisite clay in 1,4-cis polyisoprene nanocomposites were monitored during uniaxial compression. Interaction of the Fe+3 in the clay with the polymer decreases the polymer's H-1 spin-lattice relaxation time constant (T-1). In some of the nanocomposites, the increase in the interfacial area of the clay platelets was observed by a decrease in the polymer's T, with successive amounts of strain. The observation of these changes with static H-1-NMR is limited by the dispersion of the clay. (c) 2005 Wiley Periodicals, Inc.