|The ingestion of methylmercury (MeHg) has been found to adversely affect primate and human visual fields and contrast sensitivity (Choi, Cho, & Lapham, 1981; Clarkson, 1989; Gilbert & Grant -Webster, 1995; Merigan, 1980; Rice, 1994; Rice & Gilbert, 1982). The frequency at which a flickering stimulus is perceived has been related to both phenomena and to possible damage to the parvocellular or magnocellular visual neural systems. The rats visual system, although different from the human visual system contains parvocellular regions related to their visual perception. A series of experiments were conducted to develop a method for testing the rats visual perception to a flickering stimulus. A behavioral discrimination procedure was developed using four Long Evans male rats. Three testing methods were used. No significant difference was found between or within subjects or between and within methods for the frequency at which a flickering stimulus is perceived as a steady stimulus.