The mechanisms by which perivascular adipose tissue (PVAT) can reduce vascular contractility remain to be elucidated and may underlie the associations of obesity with hypertension, insulin resistance and cardiovascular disease. This study investigates the effects of aldosterone and obesity in isolated rat aorta. Healthy and obese male rats were killed by stunning and cervical dislocation. The mesenteric bed was removed and arteries dissected with and without PVAT. Arteries were mounted on a wire myograph and were constricted with 60 mM KPSS. Cumulative concentration responses (10−9–10−5 M) to norepinephrine (NE) were performed before and after 10 min incubation with aldosterone (5 nM). Endothelial integrity was confirmed by relaxation to 10−5 M acetylcholine. Responses are expressed as mean (±SEM) percentage of KPSS constriction and analysed using two-way ANOVA. PVAT (n=10) significantly (p<0.05) reduced constriction in healthy vessels (PVAT: 81 (20)% vs no PVAT: 140 (27)% at 10−5 M NE). The anticontractile properties of PVAT are abolished (n=6) in the presence of aldosterone (PVAT: 53 (24)% vs no PVAT: 62 (35)% at 10−5 M NE). Aldosterone significantly reduced tension (p<0.05) compared with no PVAT controls. The anticontractile properties of PVAT (n=6) are absent in arteries from obese animals (PVAT: 105 (33)% vs no PVAT: 91 (15)% at 10−5 M NE); however, in the presence of aldosterone (n=6) constrictions are significantly increased (p<0.05) in arteries with (PVAT: 133 (49)% vs no PVAT: 89 (18)% at 10−5 M NE).These results demonstrate that obesity and aldosterone impair the anticontractile effects of PVAT. Aldosterone reduces contractility in healthy arteries but increases contractility in obese arteries.