['Recent reports have shown elevated concentrations of serum cystatin C (CC) in patients with solid tumours. The aim of our study was to investigate whether patients with proliferative haematological disorders have increased serum concentrations of CC compared with normal subjects.', 'Full blood count, serum CC, beta2-microglobulin (beta2M) and serum creatinine were determined in 27 apparently healthy subjects and 35 patients with proliferative haematological disorders. Creatinine clearance was calculated using the Cockroft-Gault formula.', 'CC and beta2M showed a significant correlation with each other (r=0.96, P<0.0001). Serum beta2M (P=0.001) and the serum beta2M:CC ratio (P=0.001) were significantly higher in the patients with normal renal function than in controls, but serum CC was not significantly different (P=0.08). CC did not show a significant correlation with blood count parameters.'] Is serum concentration of cystatin C affected by cellular proliferation in patients with proliferative haematological disorders?