To study the oscillatory potentials in early diabetic retinopathy the authors developed a new power measurement based on the fast Fourier transform. Three groups totalling 46 patients were examined, varying from nonvisible to preproliferative diabetic retinopathy. The oscillatory potentials expressed in microwatts were measured under scotopic and photopic conditions. The data of the three groups are compared with those of a group of 22 normal individuals. The oscillatory potential power measurement appears to be a reliable method in detecting diabetic retinopathy at an early stage.