BACKGROUND: Interleukin 1β (IL 1β) levels are associated with prognosis in heart failure. The cardiac adrenergic activity as assessed by metaiodobenzylguanidine (I123 MIBG) scintigraphy along with exercise parameters are important predictors of prognosis. The relationship between these variables is not fully established. OBJECTIVE: To evaluate the association of IL 1β levels with exercise and I123 MIBG parameters. METHODS: Cross-sectional observational study evaluating 25 consecutive patients with heart failure and ejection fraction lower than 45% by means of: determination of IL 1β levels; I123 MIBG parameters [early and late heart/mediastinum ratio, washout rate (WO)]; and treadmill exercise test using the ramp protocol. RESULTS: The patients were divided into two groups according to their IL 1β levels (normal vs. increased). The group with increased levels showed lower double-product reserve (DPR); lower functional capacity (FC); slower heart rate recovery at the first (HRR 1º) and second minute (HRR 2º); and higher WO. In the univariate analysis, all variables correlated with IL 1β; DPR: r = 0.203, p = 0.024; FC: r = 0.181, p = 0.034; HRR 1º: r = 0.182, p = 0.034; HRR 2º: r = 0.204, p = 0.023; WO: r = 0.263, p = 0.009. In the multivariate analysis, only WO maintained a significant correlation (r² = 0.263, p = 0.009). CONCLUSION: Adrenergic overactivity was the main determinant of IL 1β levels, thus demonstrating that an excessive sympathetic activity influences the systemic inflammatory response. Exercise test variables were not able to identify patients with high IL 1β levels.