In the rats administered mercuric chloride (1mg/kg/48 hrs i.p.), it was found that LDH$_{1}$ and LDH$_{2}$ were increased in heart, brain and kidney as well as LDH$_{5}$ increased in liver and muscle in the duration of sixteen days. After the sixteen days of administration, the LDH isozyme patterns in the above mentioned organs were found to be irregularly changed. Considerable amount of mercury accumulation in liver and kidney were found, and especially the mercury accumulation in kidney was notable.