Contrast sensitivities for a range of sinusoidal grating frequencies and a range of single bar widths were measured in 4 subjects. Unadapted contrast sensitivity was compared with that following adaptation to sinusoidal gratings of 5.5 or 16 cycles/deg, or bars of 7.5 or 1.25 min width, at 1.5 log units above threshold. Adaptation to both these sinusoids produced frequency specific elevation of threshold for sinusoids, whereas adaptation to 5.5 cycles/deg gratings uniformly elevated the bar threshold, and adaptation to 16 cycles/deg did not affect the bar threshold. Adaptation to bars produced no width specific adaptation in the bar sensitivity function, but elevated the threshold for bars of all widths, as well as elevating the threshold for sinusoids of all frequencies. Bar width and spatial frequency are not equivalent, and there is no evidence for width selective channels. Bars seem to be detected when their frequency components most easily detected by the visual system (near 5 cycles/deg) rise above their independent thresholds.