Stiles developed a method for estimating whether rod-photoreceptor activity contributed to color-matching data. This method requires knowledge of the rod threshold at the illuminance levels of lights being viewed. Stiles suggested that the Aguilar and Stiles scotopic threshold-versus-illuminance (TVI) curve could serve as a convenient approximation of the rod threshold. Stiles＇ method was intended for use in color-marching experiments where the stimuli are presented side by side, but, in the Aguilar and Stiles experiment, detection thresholds were measured for temporally, pulsed lights. This study, compares rod-sensitivity with detection and side-by-side adjustment tasks. The illumination level of the rest and background light was kept below the absolute threshold of the short-wavelength sensitive cones, because there is evidence that cone signals may interact with the scotopic TVI function. The threshold data fell mainly within the range of the Aguilar and Stiles observers. There were two notable deviations from the Aguilar and Stiles curve (1) consistent with previous reports, the scotopic TVI function had a slope shallower than the Aguilar and Stiles curve when measured with a short-wavelength background (2) thresholds measured from a dark surround with a spatial adjustment task were higher than the Aguilar and Stiles thresholds even though the slopes were the same.