INTRODUCTION Patients with chronic kidney disease (CKD) are particularly susceptible to cardiovascular disease (CVD). Increased synthesis of endogenous monounsaturated fatty acids (MUFAs) by stearoyl-CoA desaturase-1 (SCD1) might predispose to cardiovascular complications. OBJECTIVES The aim of this study was to examine the serum MUFA content in patients at subsequent stages of CKD, and to evaluate associations between MUFA content and SCD1 activity, patients' diet, and cardiovascular risk. PATIENTS AND METHODS Serum fatty acid composition was evaluated in 177 patients with subsequent stages of CKD (1-2, 3a, 3b, 4-5, hemodialysis, peritoneal dialysis, and after kidney transplantation), and in 30 healthy controls. Gas chromatography-mass spectrometry was used for the measurement. RESULTS Serum MUFA content was shown to increase with subsequent stages of CKD and to be correlated with various risk factors of CVD, including serum triacylglycerols, HDL cholesterol (P <0.01), and high-sensitivity C-reactive protein (P <0.05). Moreover, also the prevalence of CVD was shown to increase with CKD progression. Estimated SCD1 activity was associated with serum MUFA content (P <0.01), but no association was found between dietary MUFA intake and serum MUFA levels. CONCLUSIONS Our results indicate that the elevation of serum MUFA levels in CKD patients may contribute to an increased risk of CVD during CKD progression, mainly due to increased endogenous MUFA synthesis by SCD1.