Mean platelet volume (MPV) and count (PLT) were assessed in patients with moderately affected liver function. PLT was significantly decreased in patients with liver disease (197 X 10(9)l-1 +/- 87 (SD), no. = 79) compared with that of controls (273 X 10(9)l-1 +/- 53 (SD), no. = 37, P less than 0.001). MPV in patients with liver disease (9.25 +/- 1.14 fl) was significantly lower than that of controls (10.52 +/-0.74 fl, P less than 0.001). In control subjects MPV and PLT were inversely correlated (r = -0.48, P less than 0.01), but statistical significance was not found in patients with liver disease (r = -0.2, 0.05 less than P less than 0.1). It is concluded that the low MPV and PLT are compatible with an intravascular activation (loss of granules) and increased consumption of platelets, which may take place in the diseased liver even in patients with a relatively well preserved liver function.