Selective processing of relevant aspects of our environment is crucial for goal-directed behavior. In the visual cortex, neurons encoding attended stimuli show synchronized activity within the γ-frequency band (30 – 100 Hz). Given this rhythmic nature of neuronal activity, with alternating phases of enhanced and diminished excitability, effective information transmission should not only necessitate synchronization of oscillatory activity but should critically depend on the phase difference between sender- and receiver neurons’ γ-activity. To test this, we simultaneously recorded neuronal activity in the granular and supragranular layers of V1 in two macaques (Macaca mulatta). The monkeys performed a task with visual stimuli characterized by randomly changing luminance with every screen frame (flicker). We quantified the causal influence of the stimulus on neuronal activity by calculating the spectral coherence between the time courses of stimulus luminance and CSD for periods characterized by different but constant γ-phase differences. We found that the transmission of flicker-tagged stimulus information to supragranular populations strongly depended on the γ-phase relations between granular sender- and supragranular receiver populations. Spectral coherence between stimulus flicker tag and supragranular CSD was twice as high during periods with the preferred γ-phase relation between granular and supragranular layers than during periods with other phase relations. This demonstrates the functional relevance of phase relations between neurons’ gamma-oscillatory activity for information routing and stimulus processing and underscores the potential of their modulation as a mechanism for selecting relevant and blocking irrelevant information. This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 331514942.