Lipopolysaccharide-binding protein (LBP) is a reliable indicator of serum lipopolysaccharide (LPS) concentration. Raised levels of circulating LPS can trigger an increase in chronic pro-inflammatory cytokines, which may mediate the development of insulin resistance and obesity. Psoriasis is a chronic inflammatory skin disease that has been associated with metabolic syndrome. We aimed to study the expression of LBP in patients with psoriasis treated with narrowband ultraviolet B phototherapy, and controls matched by age, gender and body mass index (BMI). We did not find any differences in serum LBP concentration between patients and controls, and serum LBP did not correlate with the Psoriasis Area and Severity Index. However, patients with psoriasis and metabolic syndrome had higher serum concentration of LBP than controls. Furthermore, correlation with BMI and apolipoprotein B was present in controls, but not in patients with psoriasis. Serum LBP level did not change significantly after treatment with phototherapy. © The Author(s). CED © 2012 British Association of Dermatologists.