Objective: This study investigated the biochemical,histopathological and physiological effects of Citrullus colocynthis on peripheral neuropathy in rats with streptozotocin (STZ)-induced diabetes.Methods: Seventy adult male Sprague-Dawley rats were included in the present study.Diabetes was induced in 60 rats,with a single intraperitoneal injection of STZ (65 mg/kg).After 4 weeks,the diabetic rats were assessed for neuropathy.Then,the diabetic rats with neuropathy were randomly divided into 6 groups for a 4-week treatment with gabapentin,oral administration of C.colocynthis fruit pulp powder (100 and 300 mg/kg per day),topical preparations as oil-based solution and ointment,or placebo.Changes in metabolic,physiological,biochemical and histological parameters were considered as treatment outcomes.Results: Metabolic outcomes (body weight and blood glucose level) were improved in the C.colocynthistreated groups as compared to placebo.Tail-flick and hot-plate tests also had lower latency in the C.colocynthis-treated groups.Measurement of oxidative stress markers (malondialdehyde,superoxide dismutase and catalase) showed the antioxidant effect of C.colocynthis.Histological evaluation of the sciatic nerve showed that C.colocynthis decreased the number of demyelinated and degenerated nerve fibers.Among the C.colocynthis-treated groups,the one receiving 100 mg/kg power per day orally had the best treatment outcomes.Conclusion: The present study showed that C.colocynthis fruit,through its antioxidant and hypoglycemic activities,has a positive effect in the treatment of diabetic neuropathy.