Following instillation of four drops of a solution of 0.2% cyclopentolate hydrochloride, 1% phenylephrine hydrochloride, with 3% polyvinylpyrrolidone in buffered isotonic base with 0.5% chlorbutanol as a preservative (cyclomydril), an 82-year-old man showed a decompensation of a previously compensated chronic dementia. It is postulated that he became delirious as reported in other cases following administration of 1% or 2% cyclopentolate. Further, his failure to recover the status quo ante was felt to represent a more general phenomenon; namely, the inability to regain coping mechanisms established at a time when the mental apparatus was capable of a higher order of function.