Purpose: To determine why Polish patients included in the International Stroke Trial (IST) had a higher early case fatality than patients from other countries. Methods: Of 19435 patients randomised to IST, 17 370 had CT or autopsy-confirmed ischaemic stroke. We compared the baseline clinical state and 14-day case fatality of patients randomised in Polish centres with those from all other IST countries. We examined: age, gender, presence of atrial fibrillation (AF), conscious level, neurological deficit, cause of death and aspirin use in the 3 days before stroke. Results: In Poland, the 14-day case fatality rate was significantly higher than in other IST countries (13% vs. 9.6%; odds ratio, OR, 1.5, 95% confidence interval, CI, 1.2-1.9). In Poland, a significantly higher proportion of deaths was attributed to coronary heart disease (2.5% vs. 0.7%) and pulmonary embolism (1.0% vs. 0.4%). Polish patients had higher percentage of AF and drowsiness, but were younger. When these factors were adjusted for, Polish patients still had approximately a 57% higher risk of death within 14 days compared with other countries. A logistic regression analysis revealed that an increased risk of death within 14 days in Poland compared to other IST patients was present among patients younger than 75 years (OR 1.7; 95% CI 1.3-2.4), females (OR 1.8; 95% CI 1.3-2.5), patients who were alert at onset (OR 2.4; 95% CI 1.7-3.4), with partial anterior circulation syndrome (PACs) (OR 2.0; 95% CI 1.4-2.8) or lacunar syndrome (LACS) (OR 2.4; 95% CI 1.1-5.0) and without AF (OR 1.8; 95% CI 1.3-2.4). Polish patients were less likely to have been on aspirin before their stroke than other countries (7.6% vs. 20.8%). Conclusion: The 14-day case fatality was significantly higher in Poland than in other countries in IST. Part of the increase was due to greater stroke severity in the Polish patients. However, differences persisted even after adjustment for baseline stroke severity. Several factors may have contributed the excess: poor attention to treatment of cardiovascular disease, less attention to treatment of secondary complications of stroke and some other-as yet unidentified-factor specific to Poland. (C) 2002 Elsevier Science B.V. All rights reserved.