Zinc and iron levels were studied in mice with early (pre/neonatal) exposure to phenobarbital, as the levels of these trace metals are known to be correlated with specific behaviors shown in our previous and present experiment to be affected by early phenobarbital administration. Mice were exposed to phenobarbital prenatally or neonatally. At adulthood they showed marked reduction from control in all parameters of eight-arm maze performance (P less than 0.001). Since zinc is known to be correlated with this behavior, it was subsequently studied in barbiturate exposed animals. The differences between barbiturate exposed and control offspring for zinc levels in plasma, brain and hippocampus did not reach statistical significance. Our previous studies have shown that the number of dopamine receptors and the resulting apomorphine-induced climbing behavior is altered after early exposure to phenobarbital. The effect of iron level on dopamine receptors is now well established. Subsequently, a group of mice were tested for iron levels in their brain and liver. No significant differences were found. It is suggested that deficits in the hippocampal behaviors, mainly eight-arm maze, after early exposure to phenobarbital are not related to changes in zinc levels. Similarly, early phenobarbital-induced alternation in dopamine receptors and the resulting dopaminergic behaviors are not related to changes in iron levels.