To investigate the nerve conduction and P300 event-related potentials (ERPs) alterations in non-insulin-dependent diabetes mellitus (NIDDM) with peripheral diabetic neuropathy (PDN) treated with gamma linolenic acid (GLA) and acetyl l-carnitine (ALCAR). Forty-five NIDDM patients who were diagnosed as PDN according to peroneal nerve motor and sural nerve sensory conduction were given either 360 mg/day GLA or 360 mg/day GLA+1gr/day A LCAR during six months. Nerve conductions and P300 latencies of all patients were recorded before and after the treatment. In both groups, the improvement in the nerve conductions and P300 latencies was statistically significant after the treatment (p<0.001). But the improvement recorded in all three parameters was more significant in the group treated with GLA+ALCAR (p<0.001). In GLA group, peroneal nerve motor conduction increased by 2.3%, sural nerve sensory conduction increased by 4.1%, P300 latency decreased by 0.7%, in the GLA+ALCAR group these results were 6.4%, 8.3% and 1.6% respectively. These findings suggest that GLA is an effective and safe agent in PDN and in the complications of diabetes on the central nerve system, and the combination of GLA with ALCAR is increasing this effectiveness.