INTRODUCTION: Ultrasonic vocalizations (USV) are means of communication between rats. We are studying them by presenting USV or artificial tones from a speaker (playback experiments) and observing vocal (rat’s own USV), behavioral, and cardiovascular (heart rate, HR) reactions. We used Wistar rats, which are common in USV experiments, and SHR (spontaneously hypertensive rats), whose USV habits have not been investigated. AIM(S): We are especially interested in the role of the autonomic nervous system. Therefore, we are investigating the impact of fear conditioning which affects autonomic balance in Wistar rats and SHR with higher activity of the sympathetic system. METHOD(S): Three different protocols were used (1x, 6x, or 10x; 1 mA, 1 s shocks) and later, the animals were presented with 50 kHz (appetitive) or 22 kHz (aversive) USV. On the day of conditioning, Wistar rats emitted 22 kHz USV immediately after the first electric impulse, while SHR remained silent typically to the sixth-eight shock. Levels of freezing were similar in both strains. On the following day, during ultrasonic signals presentation, after 50 kHz USV playback, SHR did not show a rise in HR nor an increase in their own USV emission, which were both observed in Wistar rats. Both strains responded to 22 kHz USV by a decrease in HR, independently of fear protocol. During the conditioning test, the day after playback experiments, Wistar rats showed lower HR following 1x conditioning. Also, a dramatic rise in numbers of USV was observed in some of 6x animals. Only the HR of 1x conditioned Wistar rats was lower than in the control (not conditioned) group (HR of 6x and 10x Wistar rats did not differ from control group), while in SHR, all conditioned groups tended to have higher HR than controls. CONCLUSIONS: We confirm that fear conditioning affects the reaction to ultrasonic signals in SHR and Wistar rats. Presumably the autonomic nervous system participates in reactions to USV playback; however, further research with pharmacological agents is essential. To our best knowledge, these are the first studies about USV in SHR. FINANCIAL SUPPORT: This work was supported by National Science Centre, Poland, grant no. 2015/19/B/ NZ4/03393.