Objectives: Neurological deterioration (ND) after ischaemic stroke has been indicated as an independent risk factor for poor outcome. Previous studies have focussed on ND within the first few days after symptom onset, but many patients are likely to experience deterioration outside of this time frame. We aimed to investigate the predictors of ND during hospitalisation. Methods: Data were obtained from the Chinese Intracranial Atherosclerosis (CICAS) Study, and patients who were diagnosed with ischaemic stroke and arrived at the hospital within 72 hours after symptom onset were included in the present study. Neurological deterioration was defined as an increase in the National Institutes of Health Stroke Scale (NIHSS) score of >= 2 points at discharge compared with admission. MR angiography (MRA) andduplex colour Doppler ultrasound were used to document the presence of intracranial or extracranial artery stenosis. Intracranial artery stenosis was defined as a reduction in the artery diameter of >= 50% on MRA. Multivariate analyses were conducted to determine the potential predictors of ND during hospitalisation. Results: Of the 1996 patients included in this study, 84 (4.21%) developed ND during hospitalisation. Compared with non-ND patients, ND patients showed higher rates of pneumonia (25.0 vs 9.5%, P<0.001), urinary infection (7.1 vs 1.2%, P<0.01), stroke recurrence (14.3 vs 1.9%, P<0.001), watershed infarct (15.5 vs 5.4%, P=0.002), intracranial internal carotid artery (ICA) stenosis (11.9 vs 6.0%, P=0.041), middle cerebral artery (MCA) stenosis (39.3 vs 22.0%, P<0.001) and basilar artery (BA) stenosis (16.7 vs 7.1%, P=0.011). Multivariate analysis indicated that watershed infarcts (OR, 2.85; 95% CI, 1.04-7.81), MCA (OR, 2.23; 95% CI, 1.17-4.25) and BA (OR, 2.86; 95% CI, 1.19-6.87) stenosis or occlusion were independent risk factors for ND, as was pneumonia (OR, 3.4; 95% CI, 1.46-7.9). Discussion: Patients with watershed infarcts and MCA or BA stenosis or occlusion should be monitored closely, and various therapeutic strategies should be administered simultaneously to prevent pneumonia during hospitalisation.