The effect of chronic dietary lead exposure on brain nigrostriatal, mesolimbic and mesocortial systems was studied. The results show no modification of the dopamine receptors measured either as dopamine sensitive adenylate cyclase or as [3H]spiroperidol binding. On the other hand, dopamine synthesis seems to be reduced in striatum, unaffected in substantia nigra and increased in nucleus accumbens and in the frontal cortex. The increase of DA synthesis observed in some brain areas might be involved in determining the hyperactive behaviour that follows lead intoxication.