The internal and surface chemical compositions of three sodium starch glycolate (SSG) products, Explotab, Primojel and Vivastar P were studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), time of flight secondary ion mass spectrometry (TOF-SIMS) and 23Na nuclear magnetic resonance spectroscopy (NMR). The surfaces of Explotab and Primojel contained very distinct features containing Na and Cl, however, Primojel also contained features which contained Na which may reflect the presence of Na glycolate and/or Na citrates. Vivastar P contained relatively few surface Cl containing features. Analysis of cross-sections of the particles showed that Na appeared to be uniformly distributed throughout the particles of all the products. Additionally, there was a significant concentration of Cl in the periphery of Explotab and Primojel. In the case of Vivastar P, significant levels of Na and Cl were detected in the internal regions of the particles which, together with 23Na NMR, suggests that NaCl is uniformly distributed within Vivastar P. 23Na NMR also suggested that the ratio of organic Na to NaCl was considerably lower in Vivastar P than Primojel and Explotab. Overall, even though all these three products satisfy the pharmacopeial descriptions of SSG, these studies suggest that Primojel and Explotab exhibit different chemical compositions to Vivastar P. Since the three products studied are reported to be prepared from potato starch, the apparent differences in chemical composition probably reflect the different manufacturing processes used, however, batch to batch variations may account for some of the subtle differences.