Aim of this thesis was to find out if the rheological oscillatory test is suitable to use for use as a measuring method to determine the stiffness of hydrogels. Due to the softness of hydrogels the measurement of the Young’s modulus by compression test is limited, as the softer hydrogels do not maintain their shape. The compression test is suitable measuring method for hydrogels that have higher cross-linker concentrations. Materials that where used in this thesis were gellan gum and hyaluronic acid based hydrogels. In gellan gum hydrogels the cross-linker was spermine or spermidine and in hyaluronic acid hydrogels the cross-linker was polyvinyl alcohol. The total number of samples was 180. The rheological properties were measured by a rheometer. The measuring program that was used was oscillatory test. The amplitude sweep was used to define the linear viscoelastic (LVE) range for hydrogels. From the LVE range, the storage modulus and the loss modulus were determined. The complex shear modulus was then calculated by using the storage and the loss modulus. Additionally, the frequency sweep from LVE range was measured. The stress-strain curves for hydrogels were determined by a compression test. The Young’s modulus was calculated from the slope stress-strain curve. As an observation the oscillatory test proved to be a more accurate measuring method than the compression test. The anisotropy of the sample structure caused variation of results and higher standard deviations. The compression test results were not affected by the anisotropy of the samples. The rheological measuring method turned out to be suitable for measuring the stiffness of the softer hydrogels. For the stronger hydrogels, on the other hand, the results had a high standard deviation. The reason for the high standard deviation is the anisotropy of the sample structure. The rheological moduli for gellan gum hydrogels were lower and the standard deviation higher than for the hyaluronic acid hydrogels. As a conclusion from both measuring methods, the stiffness of the hydrogels became higher when the cross-linker concentration increased. The rheological measurement method was found to be suitable for the softer hydrogels. However, for the hydrogels with the higher cross-linker concentration and the fast gelation time, the rheological measuring method needs further studies.