INTRODUCTION: Heavy metals are frequently used in the preparations of traditional/folk medicines. One such preparation in Ayurveda is Nagabhasma, in which lead is the main ingredient. Lead is non-essential element to the human body and is known toxic substance to many organ systems. However, it is claimed that, the highly toxic metallic lead will be converted into health beneficial organo-metallic compound when raw lead is subjected to various traditional methods of purification during preparation as mentioned in the ancient medicinal system. AIM: The present study is designed to evaluate the effect of such detoxification of lead in various stages of authentically prepared Nagabhasma on the learning and memory. MATERIALS AND METHODS: Using half of the human equivalent doses of traditionally prepared Nagabhasma, at intermittent stages of its preparation were fed orally to healthy Wistar rats for 30 days. After treatment, the immediate effect and residual effect after 2 months was evaluated by subjecting them to passive avoidance test. Then rats were sacrificed and hippocampus was collected for histopathological evaluation. RESULTS: Pure lead treated animals showed deficit in learning and memory which is indicated by spending more time in the dark compartment in passive avoidance test. However, animals treated with stage 1 to 4 Nagabhasma showed gradual increase in the memory and learning. This observation is substantiated by the findings of the histopathology of the Cornu Ammonis (CA) region of hippocampus. CONCLUSION: The results of the present study indicate that, the metallic toxicity of the lead used in the preparation of bhasma was gradually decreased from stage 1 to stage 4 of preparation. Therefore, the traditional way of preparing the metallic bhasma is very critical in eliminating the possible health hazardous metallic lead toxicity.