Psychiatric patients and normal controls were compared for pupillary responsivity, under dark-adapted conditions, using single pulses of light presented via a Ganzfeld. Data were collected with electronic equipment, and averaging techniques were used in the analysis of continuous response curves. Results showed that recently admitted patients tend to have slightly smaller pupillary diameters than normals, when at rest, and exhibit substantially attenuated reactivity to light stimulation. Consideration is given to possible artifacts, and findings are interpreted in terms of the known physiological characteristics of pupillary innervation.