Successful behavior requires the attentional selection and preferred processing of behaviorally relevant sensory information. Painful stimuli are of utmost behavioral relevance and can therefore involuntarily affect attentional resources and interfere with ongoing behavior. However, the neuronal mechanisms which subserve the involuntary attentional effects of pain are largely unknown yet. Here, we therefore investigated the neuronal mechanisms of the attentional effects of pain by using electroencephalography during a visual attention task with the concurrent presentation of painful stimuli. Our results confirm that painful and visual stimuli induce gamma oscillations over central and occipital areas, respectively. Pain-induced gamma oscillations were correlated with pain-induced changes in visual gamma oscillations. Behaviorally, we observed variable effects of pain on visual reaction times, yielding an increase of reaction times for some subjects, as well as a decrease of reaction times for others. Most importantly, however, these changes in visual task performance were significantly related to pain-induced changes of visual gamma oscillations. These findings demonstrate that the variable attentional effects of pain are closely related to changes in neuronal gamma oscillations in the human brain. In the hypervigilant state of chronic pain, maladaptive changes in the attentional effects of pain may be associated with abnormal changes in neuronal gamma oscillations. Our findings may thus contribute to the understanding of the neuronal substrates of pain in health and may open a new window towards the understanding of pathological alterations of the pain experience in chronic pain syndromes.