A Short review on different models describing the occurrence of interfacial instabilities and their influence on mass transfer is given. The stability behaviour of different liquid-liquid systems are investigated with two different apparatus. The holographic interferometry and the laser-doppler-anemometry (LDA) were used to visualise and quantify interfacial convections. The experiments were carried out at flat moving interfaces. The onset of instabilities is influenced not only by the direction of mass transfer and the concentration difference between the two phases but also by the velocity near the interface and the relative direction of flow of the phases. The interfacial instabilities affect the concentration profiles in the bulk phases, too.