To study how adaptation to spatial frequency patterns affects temporal sensitivity in vision, observers were selectively adapted for 4 min to either a high- or a low-spatial-frequency sinusoidal grating (12 and 2 cpd, respectively). Their sensitivities to modulation of a blurred patch at high or low temporal frequencies (12 Hz and 2 Hz, respectively) were measured, before and after the adaptation period, by using the yes/no task of signal detection theory. The data consistently indicated that spatial adaptation differentially affected the observers' sensitivities to temporal signals. Specifically, when the observers were adapted to low spatial frequencies, their sensitivity to low temporal frequencies was reduced; when they were adapted to high spatial frequencies, their sensitivity to high temporal frequencies was increased. These results have implications for the psychophysical measurements of temporal and spatial sensitivity, as well as for the issue of the separability of spatial and temporal properties of individual channels.