The computational power of dendrites has long been predicted using modeling approaches, but actual experimental examples of how dendrites solve computational problems are rare. We have addressed this question by performing direct patch-clamp recordings from the dendrites of pyramidal cells in mouse primary visual cortex during sensory processing. Visual stimulation triggered regenerative events in the dendrites of layer 2/3 pyramidal cells, including high-frequency bursts of dendritic spikes. These events were orientation tuned and suppressed by either hyperpolarization or intracellular NMDA receptor blockade. Both these manipulations also decreased the selectivity of subthreshold orientation tuning measured at the soma, thus linking dendritic regenerative events with somatic orientation tuning. These results suggest that dendritic spikes triggered by visual input contribute to a fundamental cortical computation: enhancing orientation selectivity in visual cortex.