Results of experimental investigations on three crude oils are presented in this thesis. A Spinning drop video tensiometer (Dataphysics SVT 20N) was used to measure interfacial tension (IFT) between crude oil and distilled water. Additional preliminary experiments were performed to determine the IFT at the interface between decane and aqueous phase to establish a constant reference IFT value for the system. The average IFT value of decane measured by the instrument is of 38mN/m. The highest interfacial tension was observed for the „Crude oil B”. The average value is 12.4 mN/m. The “Crude oil C” is characterized by the IFT of 6-7 mN/m. The lowest IFT of 0.8-1.2 mN/m was obtained for the “Crude oil A”. For all examined crude oils, the IFT decreased in function of time. It was found that the dynamic IFT behaviour depends on the type of crude oil and viscosity. Oil samples studied have different IFT reduction rates. The objectives of this thesis were to perform standard IFT measurements and develop the methodology for further investigations. Test studies were performed to understand the effect of temperature and rheological behaviour of oils. Oscillatory tests for the „Crude oil A” showed that the observed fluctuations (jumps) in the IFT curve are of an artificial origin and are related to the movement of the drop. In addition, a methodology for the preparation of oil samples and instruments for the IFT measurements was developed. The obtained results are useful for understanding the IFT behaviour of oils and can be applied for further investigations.