The influence of male hormones in the reflex control of the cardiovascular system has been investigated lately. Testosterone has been shown to improve the baroreflex-madiated bradycardia, but high doses of anabolic-androgenic steroids (AAS) have the opposite effect. Cardiopulmonary reflex is blunted under AAS influence, but surprisingly, no study has already investigated the physiological role of testosterone on this reflex (the Bezold-Jarisch Refelx-BJR). We investigated the effect of castration, in different periods after orchidectomy (OVX), in the BJR control of diastolic arterial pressure (DAP) and HR. Male Wistar rats were divided into six experimental groups, as stated in Table 1. OVX was performed under sodium pentobarbital anesthesia (50mg.kg-1, intra-peritoneal, Crystal, Brazil). The experiments were performed in accordance with the ethical principles for animal experimentation by the Brazilian College of Animal Experimentation and were approved by our Institutional Ethics, Bioethics and Animal Welfare Committee (Protocol 118/2010). BJR was analyzed by measuring the bradycardia and hypotension responses elicited by phenyldiguanide administration (1.5-24 µg/kg). Mean arterial pressure (MAP) was assessed and myocyte hypertrophy was determined by morphometric analysis. Testosterone and 17β-estradiol were measured in blood samples. Table 1 shows that the reduction of BJR control of DAP starts after 72h of OVX and after 7 days in the control of HR. After 21 days of castration the BJR reach its lowest capacity to control DAP and HR. The levels of testosterone were reduced in orchidectomized groups (OVX24h:0.26±0.02; OVX72h:0.18±0.01; OVX7D:0.12±0.01; OVX14D:0.08±0.01; OVX21D:0.01±0.00 ng/mL; p<0.01) in comparison with SHAM (0.47±0.12 ng/mL). Blood 17β-estradiol (SHAM:0.022±0.003; OVX24h:0.023±0.002; OVX72h:0.028±0.003; OVX7D:0.025±0.003; OVX14D:0.023±0.001; OVX21D:0.026±0.002 ng/mL), MAP (SHAM:104±3; OVX24h:101±5; OVX72h:108±4; OVX7D:110±4; OVX14D:107±5; OVX21D:105±4 mmHg), and myocyte hypertrophy (SHAM:5.3±0.4; OVX24h:4.9±0.3; OVX72h:4.8±0.3; OVX7D:5.6±0.5; OVX14D:5.1±0.4; OVX21D:5.3±0.4 myocyte nuclei/high power filed) did not change among the experimental groups. We conclude that castration of male animals caused decrease in testosterone levels and reduced sensitivity of BJR, indicating a positive physiological role of testosterone on functioning of this reflex.