Accommodative responses to microstimulation of the superior colliculus (SC) of cats were investigated by measuring dioptric changes of the eye with a high-speed infrared optometer. Lens accommodation was elicited by low-current stimuli (< or = 20 microA) of the rostral portion of the SC, which corresponds to the representation of the central visual field. The low-threshold area for evoking lens accommodation was distributed from the superficial to intermediate layers of the SC. The latency of accommodative responses was 198.3 +/- 34.6 msec (mean and SD). The duration of accommodation was highly correlated with the duration of stimulation. These findings suggest that the SC plays an important role in the control of lens accommodation.