Hematocrit, total white cell and platelet counts, plasma urea and creatinine concentrations were estimated in 291 patients (mean age 70 +/- 12 years) admitted consecutively over a 6-month period to a district general hospital with acute stroke. Urinary albumin/creatinine ratio was also determined in a subgroup of patients during a follow-up visit 3 months after ictus. Results were compared with those from age- and sex-matched community controls. Total white cell count was elevated in all types of stroke compared with values from control subjects. Platelet count, plasma urea and creatinine concentrations were higher and the plasma albumin/globulin ratio was lower among patients with ischemic stroke. Elevated total white cell count, urea and creatinine, which were of prognostic significance, were found to be associated with the severity of stroke as indicated by the Glasgow coma score, and did not have any independent prognostic value. Elevated hematocrit was not shown to be a risk factor and did not have any prognostic significance. A low plasma albumin/globulin ratio, an index of plasma viscosity, was a possible risk factor for ischemic strokes. Urinary albumin/creatinine ratios in the highest quintile increased the risk of stroke 13-fold.