In order to compare visual pattern discrimination by tectal neurons in distantly related vertebrate groups, collicular cells of mice were examined for their responses to each of three simple configurational stimuli commonly used in studies of amphibians. The stimuli consisted of a large square, a horizontal bar and a vertical bar moved at various velocities. Of the recorded units (n = 51), 30–50% significantly preferred the square to the other stimuli at medium (10°/s) and high (67°/s) velocities. Approximately 10% preferred the horizontal bar at these velocities. A significant discrimination between the horizontal and the vertical bar was found in 39% of the units at a velocity of 10°/s, and in 61% at a velocity of 67°/s. These response types are very similar to those found in amphibians; therefore, it is concluded that tectal configurational sensitivity may be a plesiomorphic tetrapod character resulting from basic properties of tectal neuronal circuitry.