Merchant mariners are required to have a medical evaluation performed by a licensed medical doctor.  As part of the medical evaluation, a DOT (Department of Transportation) drug test is usually performed.  This drug test can only be performed at an approved facility that uses federal CCF (Chain of Custody Forms). In addition, a SAMSHA (Substance Abuse and Mental Health Service Administration) approved laboratory, as well as a certified MRO (Medical Review Officer), must also be used.