We studied the influence of indeloxazine hydrochloride (IH) upon photic driving responses (PDRs) elicited by a 5 Hz flickering dot pattern and red flicker stimuli. Comparisons were made from a total of 22 elderly patients. By oral IH administration, clinical improvement was found in 12 patients with cerebral arteriosclerosis (improved group), whereas it was not observed in 6 patients with cerebral arteriosclerosis, 2 patients with multiinfarct dementia and 2 patients with Alzheimer's disease (unimproved group). Before and after the IH administration, an EEG examination by the above visual stimuli was carried out in each patient; a power spectral analysis of the occipital PDRs elicited by the visual stimuli was then made. The powers of PDRs elicited by the flickering dot pattern stimulation were not significantly different in both groups; those of 10 and 15 Hz PDRs elicited by the red flicker stimulation, however, decreased significantly by the IH administration in the improved group. It was suggested that such an analysis of PDRs elicited by the red flicker stimulation might perhaps be useful as one of the indicators to evaluate the efficacy of IH.