By means of increment threshold procedures, the interrelationships between rod and cone vision is being examined in the near peripheral retina of normal and color defective observers. To date, research has shown that the spatial parameters that determine whether rods and cones interact apply during steady state adaptation and during long- and short-term adaptation. Increment thresholds obtained dark adaptation suggest that rods can influence a cone related threshold via a signal-to-noise mechanism, possibly mediated by gap junctions between the two types of photoreceptors. However, data collected during the earliest phases of light and dark adaptation suggest that more than one mechanism must underly the influence of rod and cone related signals upon one another. Future increment threshold studies should determine which of the several types of color (cone) related mechanisms interact with rods. In addition, these increment threshold studies shall be augmented by other types of psychophysical data and by means of intracellular recording.