To investigate the early changes of retinal function in diabetic patients detected by multifocal electroretinogram (mfERG). ·METHODS: The first-order kernel responses of mfERG were recorded fromeyes of 33 normal control subjects, 63 diabetic patients without retinopathy and 43 diabetic patients with background retinopathy. The response densities and implicit times of N₁ and P₁ were compared among the control, diabetic patients without retinopathy and diabetic patients with retinopathy. ·RESULTS: The response densities of N1 and P1 in central 3 rings were reduced significantly in diabetic eyes with and without retinopathy. And the implicit times of N₁ and P₁ were delayed significantly only in diabetic eyes with retinopathy. ·CONCLUSION: mfERG can detect the early changes of retinal function quantitatively in diabetic patients. Analysis of response densities and implicit times of N₁ and P₁ can reflect the progress of local retinal dysfunction in diabetes