Abstract: Objective To explore the effec to fchronic low-level lead exposure at developmental stages on learning memory and the expression of neuronal growth associated prote in 43(GAP-43) in hippocampus in rats.Methods Thirty pregnant ratswere randomly divided into 3 groups and provided with distilled water in control group and 0.05%, 0.2% lead acetate solution via drinking water in treatment groups.During pre-weaning the offspring of lead-exposed group drank leadace tate through brea stmilk, and they continued to drink the same concentration of leadace tate after weaning until 28th day after the birth(PN28).Morr is water maze was applied to observe the special learning and memory of the rats of PN 28.Western blottechnique was applied to detect the change of expression of GAP-43 in hippocam pus.Results The scores of Morris water maze task were significantly reduced in Pbexposed groups compared with that of the control group(P < 0.05).In the hippocampus, thprote in expression in Pb-exposed group(0.05% PbAc:0.258±0.089, 0.832±0.021, 0.806±0.047, 0.933±0.010, 0.593±0.004, 0.437±0.015; 0.2% PbA c:0.115±0.010, 0.590±0.018, 0.680±0.027, 0.703±0.004, 0.450±0.014, 0.325±0.007) exhibited a significant decline at the time of 1, 3, 7, 14, 21, and 28 days after the birth compared to those of the control group(P < 0.05 for all).Conclusion Chronic lead exposure results in decrease of special learning and memory and its effectmay related to the decline of expression of GAP-43 in hippocampus.