Molecular imaging enables to assess disease-associated processes at the cellular and molecular level. Nuclear medicine techniques are already available in the clinical routine. Besides these techniques, intensive research has been performed in the field of ultrasound. The development of target-specific ultrasound contrast agents in combination with modern imaging systems transformed ultrasound to a capable molecular imaging technique. It has been shown that the expression of disease-associated endothelial receptors can be assessed using targeted microbubbles, demonstrating its high value in the diagnosis of several diseases. The broad availability of suitable ultrasound systems promises a wide utilisation in the clinical routine, once clinically approved contrast agents are available. This review summarizes the basics and the current status of molecular ultrasound imaging.