Introduction: Obstructive sleep apnea is characterized by recurrent episodes of cessation of airflow due to the collapse of the airway during sleep. Patients with sleep apnea tend to have hypertension and increased sympathetic activity. Hypertension and increased sympathetic activity are also observed in spontaneously hypertensive rats. This rat strain also seems to have increased chemoreceptor drive. Objective: We investigated cardiovascular and respiratory responses induced by apnea in SHR, and the role of carotid chemoreceptors in these responses. Method and Results: Rats were anesthetized with ketamine (100 mg/kg i.p.) and xylazine (20 mg/kg i.p.). A balloon was implanted in the trachea that allows the induction of apnea without causing tracheal pain. A thoracic balloon was implanted to measure thoracic pressure, and cannulas were implanted in the femoral vein and artery. Rats received ketoprofen (2 mg /kg s.c.) after surgery. A week later, with the rat awake, 5 apneas, 15 s each, were induced. The effects of apnea were larger in SHR than in WKY. Blood pressure increased by 57±3 mmHg during apnea in SHR, and 28±3 mmHg in WKY (mean ± SEM, p < 0.05, n = 8/11). Respiratory effort increased by 53±6 mmHg in SHR, and by 34±5 mmHg in WKY. Heart rate fell by 209±19 bpm in SHR, and by 155±16 bpm in WKY. The carotid chemoreceptors were then inactivated by ligation of the carotid body artery, and apneas were induced two days later. Inactivation of chemoreceptors reduced the responses to apnea, and abolished the difference between SHR and WKY. The apnea-induced hypertension was 11±4 mmHg in SHR, and 8±4 mmHg in WKY. Respiratory effort was 15±2 mmHg in SHR, and 15±2 mmHg in WKY. Heart rate fell 45 ±16 bpm in SHR, and 49±16 bpm in WKY. Similarly, when the chemoreceptors were unloaded by giving 100% oxygen to breath, the responses to apnea were reduced, and the difference between SHR and WKY was small. Blood pressure increased by 24±6 mmHg in SHR, and 13±1 mmHg in WKY. Respiratory effort increased by 18±3 mmHg in SHR, and by 16±3 mmHg in WKY. Heart rate fell 74±17 bpm in SHR, and 93±10 mmHg in WKY. Conclusion: Chemoreceptors contribute to the responses induced by apnea both in normotensive and hypertensive rats, but they are more important in SHR, and account for the exaggerated responses induced by apnea in SHR.