This study used epididymal adipose tissue from male annexin 1 (ANXA1) null and wild-type control mice to explore the potential role of ANXA1 in adipocyte biology. ANXA1 was detected by western blot analysis in wild-type tissue and localised predominantly to the stromal-vascular compartment. Epididymal fat pad mass was reduced by ANXA1 gene deletion but adipocyte size was unchanged, suggesting that ANXA1 is required for the maintenance of adipocyte and/or preadipocyte cell number. Epididymal tissue from wild-type mice responded in vitro to noradrenaline and isoprenaline with increased glycerol release, reduced IL-6 release and increased cyclic AMP accumulation. Qualitatively similar, but significantly attenuated responses to the catecholamines were observed in tissue from ANXA1 null mice. Lipopolysaccharide (LPS) also stimulated lipolysis in vitro but its effects were muted by ANXA1 gene deletion. By contrast, LPS failed to influence IL-6 release from wild-type tissue but stimulated the release of the cytokine from tissue from ANXA1 null mice. ANXA1 gene deletion did not affect glucocorticoid receptor expression or the ability of dexamethasone to suppress catecholamine-induced lipolysis; it did however augment IL-6 expression and modify the inhibitory effects of glucocorticoids on IL-6 release. Collectively, these studies suggest that ANXA1 supports aspects of adipose tissue mass and alters the sensitivity of visceral adipose tissue to catecholamines, glucocorticoids and LPS, thereby modulating lipolysis and IL-6 release.