The influence of uniform field flicker (UFF) on the contrast threshold for stationary sinusoidal gratings was measured as a function of flicker depth. Changing from no flicker to a flicker depth of 10% produces reliable differences in threshold. Further increases in flicker depth to 60% had little additional influence. The presence of UFF produces masking with low spatial frequency stimuli as expected but at higher spatial frequencies facilitation is obtained. The results are discussed in the context of the distinction between primate Magnocellular and Parvocellular pathways.