This study was designed to investigate whether the serum concentration of the carboxy-terminal propeptide of procollagen type I (PIP), a marker of myocardial fibrosis, is related to changes of the ventricular filling dynamics in patients with early type 2 diabetes mellitus (T2DM). The T2DM group had lower mitral and tricuspid E/A ratios than the control group. Serum PIP was higher in patients with T2DM than in controls (131.1+/-45.6 vs. 109.3+/-32.5 ng/mL, p=0.039). A-Ar, an estimate of passive diastolic function, was inversely related to serum PIP levels in T2DM (r=-0.42, p=0.03). These results show a relation between LV diastolic function and serum PIP levels in early T2DM.