Background: Our understanding of bipolar disorder (BD) aetiology has advanced in recent years but our ability to translate this to improve patient care in the clinic is still limited. Methods: In this study, we have measured the concentrations of 190 different molecules using sensitive multiplex immunoassays in plasma of 17 BD patients compared to 46 matched control subjects. Results: The analyses led to the identification of 26 dysregulated proteins in BD patients compared to controls. These molecules were comprised mostly of growth factors, hormones, lipid transport and inflammatory proteins. Decreased apolipoprotein A1 has previously been associated with BD patients and this was confirmed in our study. Limitations: The present pilot study was limited by its small sample size, use of multiple drug treatments and the lack of dietary restrictions at the time of sampling. Conclusions: Future studies may increase our understanding of BD which will help to pave the way for much-needed patient stratification for better treatment outcomes. (C) 2013 Elsevier B.V. All rights reserved.