The aim of this study was to examine the magnitude of contraction of two silicone condensation-type impression materials (Xantopren and RTV)mixed in two different ways: by hand and mechanicaly, and in humid and dry conditions. A total of 56 samples were prepared: seven samples of each silicone. Specimens were poured into the brass mould until the materials was set, followed by removal and storage of samples. Using optical instrument (SIP-414 with a digital microscope) dimensional measurements were made at different time intervals after setting (2, 3, 8, 24 and 48 hours) in order to check for material shrinking. The referent value was the measure of the brass mould. T-test showed statistically significant difference in the contraction of both materials in relation to the referent value in all time intervals and all conditions and mixing methods. Comparison of the mutual magnitude of the contractions in particular conditions and mixing methods showed statistically significant difference in the contraction of RTV material in humid and dry conditions, regardless of the mixing method. Contraction of Xantopren was not statistically significant in humid and dry conditions. The contractions were always greather when the materials had been mixed in humid conditions.