Electrically evoked blink reflexes were investigated in 18 patients with hemiplegia and in 15 control subjects, using common electromyographic techniques. The EMG activities of the early and late components were quantitatively and integration. In addition, the latencies of the single components were determined. Regarding the EMG activity of the late components two major types of BR alteration could be distinguished. In type I stimulation of the clinically affected side evoked significantly decreased late components on both the affected and the unaffected sides. This pattern points to a lowered excitability of the brain stem trigeminal systems and may be associated with predominantly sensory disorders. In type II the decrease of the late components was confined to the affected side independent of the side of stimulation. This pattern may indicate a lowered excitability of the brain stem facial systems and/or of the lateral bulbar reticular formation and may be correlated with predominantly motor deficits. Both types are presumably due to a loss of facilitatory influences associated with the hemispheral lesion. Although the early component was frequently decreased on the affected side there was no consistent pattern and no relation to the alterations of the late components. The latencies of both responses, predominantly of the late ones were frequently prolonged, in particular following stimulation of the affected side. Comparison of the seemingly normal components in the patients with the corresponding control values pointed to a generally lowered blink reflex excitability in hemiplegic patients.