Purkinje shift and scotopic and photopic spectral sensitivity functions were determined for four Sooty mangabeys and five human controls using a flicker technique in a four-choice discrete trials task. Results-indicate a Purkinje shift similar in magnitude and frequency locus to that of human controls. Scotopic spectral sensitivity was almost identical to that of human controls, although both species showed reduced sensitivity relative to the standard CIE function, -at short wavelengths. Photopic spectral sensitivity disclosed enhanced sensitivity in the blue and reduced sensitivity (0.3–0.4 log units) in the red relative to human controls.