BACKGROUND: Cystatin C is a marker of renal function that appears to be associated with inflammation. The aim of the present study was to investigate whether there is any relationship between cystatin C, total and differential leukocyte count and other inflammatory markers. METHODS: Cystatin C, creatinine, high sensitivity C-reactive protein (hs-CRP), haptoglobin, ferritin, serum albumin, glucose, total cholesterol, HDL and triglycerides together with total and differential leukocyte count were determined in 490 adults (46 ± 16 years, 40% men) who underwent a typical health examination. Glomerular filtration rate was estimated by the simplified Modification of Diet in Renal Disease formula. Anthropometric and lifestyle characteristics were also recorded. RESULTS: After adjustment for demographic risk factors, comorbid health conditions and renal function, a positive and independent relationship of serum cystatin C levels with peripheral monocyte blood count (regression coefficient ± SE: 12 ± 3.38, P < 0.001) and white blood count (0.616 ± 0.278, P= 0.027) was evident. In this multiple linear regression analysis, other inflammatory markers (i.e. hs-CRP, haptoglobin, ferritin, albumin) did not seem to affect cystatin C blood levels. CONCLUSION: The results of this study demonstrated that monocytes, which play an important role in chronic inflammation and atherosclerosis, were independently related with cystatin C concentrations. This finding may provide a plausible link for the usefulness of cystatin C in predicting increased cardiovascular risk.