BACKGROUND: Recent studies show that controlled breathing improves baroreflex and heart rate variability and lowers blood pressure in hypertensive patients. OBJECTIVE: To evaluate the effects of slow breathing training on cardiorespiratory system modulation of patients (n=10, men and women, ages ranging from 45 to 60) with essential hypertension seen in an outpatient setting. METHODS: According to the study design, each patient was used as his/her own control, and data were collected before and after the intervention. The following parameters were assessed: heart rate variability (HRV), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), respirometry, chest expansion measurement, and statistical data analysis. Respiratory training was performed in 30-minute sessions held twice a week over one month using slow breathing exercises. RESULTS: Our results were as follows: a reduction in SBP, DPB, and MAP (p < 0.05 vs control); an increase in heart rate variability, as evidenced by greater RR interval variation and SDNN index; a decline in respiratory rate (p < 0.01 vs control); and an increase in tidal volume (p < 0.01 vs control) and thoracic expansibility (p < 0.01 vs control). CONCLUSION: Respiratory retraining using the slow breathing technique appears to be a useful adjunctive for cardiorespiratory control in hypertensive patients.