Mice and rats produce and perceive calls in the ultrasonic range (so-called ultrasonic vocalizations, USV). Various USV types can be differentiated on the basis of distinct acoustic features. Their occurrence is dependent on stage of development, affective state and social context. When separated from nest and littermates, young mice and rats emit isolation-induced USV, which induce maternal search and retrieval behaviour. Isolation-induced USV are used as an early marker of anxiety. Adult rats emit fear-induced USV in aversive situations such as predator exposure. They fulfil an alarm function and induce anxiety-related behaviour in conspecifics. Fear-induced USV are also used in the field of anxiety research. Finally, juvenile and adult mice and rats emit interaction-induced USV in presumably appetitive situations such as rough-and-tumble play or social investigation. As they can also be elicited by drugs of abuse, they are used in the field of addiction and depression research. They have an affiliative communicative function and induce social approach behaviour in the recipient. Focusing on the communicative function of interaction-induced USV, they serve as a measure for deficits in social behaviour and communication and hence are increasingly used in animal models for neurodevelopmental disorders such as autism.