An analysis of calls to the Maryland Poison Center was performed to assess whether a relationship exists between the moon periods and poison exposure calls. A given period was defined as the day of the lunar event +/- 2 days. Thirteen lunar cycles in which 22,079 calls occurred were analyzed. A larger proportion of total calls to the center and unintentional poisoning calls occurred during the full moon period. A significantly larger number of unintentional poisonings occurred in the full moon period compared to suicide attempts and drug abuse which occurred most frequently during the new moon period. The lunar cycle had no effect on the distribution of victim's age or sex or the location of treatment.