Hyaluronan (HA) is a high molecular weight polysaccharide prevalently dispersed within the extracellular matrix of mammalian connective tissue such as the skin, with many physical and biological functions HA formulations are currently being developed for a number of medicinal, surgical and pharmaceutical drug targeting applications. The aim of this study was to evaluate, compare and characterise various HA samples by examining the rheological properties of their gels with a non-destructive dynamic rheological test using the Carri-Med CSL UK rheometer. The viscosity-average molecular weight of HA samples was also calculated by use of U-tube capillary (grade A) viscometry.Experiments were carried out using hyaluronan extracted from rooster comb [RC] (MWt 1.3 x 10 6 ), human umbilical cord [HUC] (MWt 3-5 x 10 6 ) and three sources supplied by Hyal Pharmaceutical Corporation originating from cocks comb of MWts 600,000, 678,000 and 751,000. Each sample was loaded between a 4 cm parallel plate and subjected to a frequency sweep function up to a frequency of 1-20 Hz at a fixed stress of 5 Pa at 25 o C, and the rheological parameters G', the storage modulus and G'', the loss modulus determined. Capillary viscometry provided intrinsic viscosities for dilute HA solutions and corresponding molecular weights were calculated using the Mark-Houwink equation.For each source of hyaluronan, G' and G'' was found to be a function of HA concentration. At 2.5% w/w, G' and G'' was dependent not only upon the molecular weight but also on the source of HA, due possibly to its method of isolation and/or associated protein content. For RC and HUC, G' was always greater than G'' over the 1-20 Hz frequency range, indicating the predominant elastic nature of these particular sources of HA. Further tests showed that the rheological properties of the gel varied as a function of pH and temperature; lowering pH increased G', while higher temperatures decreased gel stability thus reducing G'.In conclusion, the use of the dynamic technique provides a suitable rheological method for evaluating as well as characterising the structural properties of HA gels, and while providing regulatory authorities with valuable information, it can also be used in the development of novel hyaluronan formulations for targeted drug delivery.