This chapter is a selective and critical review of the literature on gamma oscillations in schizophrenia and related studies in other relevant fields that pertain to the hypothesis that abnormal gamma oscillations underlie symptoms of psychosis in individuals with schizophrenia. These gamma abnormalities result from deficient recurrent inhibition, in which parvalbumin-expressing, fast-spiking inhibitory interneurons do not receive sufficient excitation from N-methyl-D-aspartate receptors, resulting in a loss of phasic control over pyramidal cell spiking and impairment of gamma generation. The evidence for this hypothesis is critically reviewed, focusing on studies in the areas of visual feature binding, auditory steady-state response, and spontaneous gamma activity. The current state of the field is discussed, and recommendations for future directions are presented.