To evaluate the effects of chromatic adaptation on spectral sensitivity at temporal frequencies within the region of high-frequency linearity, critical flicker frequency was measured as a function of red-green luminance ratio for counterphase flicker of 649- and 555-nm light. For eight observers, the relative weight of the contribution of the long-wavelength-sensitive cones to flicker detection was smaller on long-wavelength adapting fields than on middle-wavelength adapting fields even though long-wavelength-sensitive-cone modulations were high. These data indicate that chromatic adaptation can confound the interpretation of flicker-sensitivity data that are gathered with long-wavelength test lights or with equiluminant heterochromatic flicker and that there can be considerable interobserver variability in the effects of chromatic adaptation.