The purpose of the study was to investigate serum uric acid (SUA), high-sensitivity C-reactive protein (hs-CRP) and mean platelet volume (MPV) in pre-hypertensive (PH) and hypertensive (HT) children and adolescents. The study group consisted of 80 patients aged 10-19 years subdivided into PH and HT groups according to mean daytime or night-time systolic or diastolic blood pressure (BP) levels (> 90th percentile, but < 95th percentile and > or = 95th percentile, respectively). The control group (C) contained 25 normotensive subjects. Serum hs-CRP level was determined by a nephelometric method (Behring); platelets (PLTs) were counted, and MPV was assessed by a Coulter Analyzer MAXM. SUA was measured with an Hitachi instrument. The median SUA and hs-CRP levels in PH and HT subjects were significantly higher than those of the controls (P < 0.01) and were higher in the HT group than in the PH group (P < 0.05). An increase in SUA above 5.5 mg/dl was associated with an increase in hs-CRP [odds ratio (OR) 4.8; confidence interval (CI) 1.3-17.4; P < 0.01]. MPV values in the PH group did not differ from those of the controls (P > 0.05), but it was significantly higher in HT patients (P < 0.01). Serum hs-CRP and MPV concentrations were positively correlated with all BP measurements except night-time diastolic blood pressure (DBP). We demonstrated that, in HT children and adolescents, increased SUA with a parallel increase in hs-CRP and PLTs with MPV is observed. Although large, multicentre, prospective studies are needed to confirm this observation, hyperuricaemia seems to be associated with an increase in hs-CRP in PH and HT patients.