There have been reports of excellent results from the treatment of pellagrous psychoses with nicotinic acid;1 these have dealt with the more familiar mental symptoms occurring in frank or subclinical pellagra of the usual type. The present communication deals with observations made on nineteen individuals all presenting mental symptoms of somewhat similar pattern, none corresponding to the ordinary conception of pellagrous dementia. Hebetude grading into profound stupor was a feature so prominent that frontal lobe tumor was suspected in three patients, lethargic encephalitis in one and chronic subdural hematoma in a third. Delirium was present three times, agitated depression once, and one patient presented the signs of central neuritis. Signs of peripheral neuritis were not discovered, but five patients had marked deafness which disappeared under treatment; it was difficult to determine whether this transient deafness was due to failure of attention or to actual interference with the auditory mechanism.