Distribution of reference substances within a country usually presents no problems. However, when samples are to be sent to other countries, both the sender and the receiver of the goods may encounter difficulties because of the vagaries of postal and customs regulations. At present, distributors of reference substances are wasting a considerable portion of their resources in seeking information concerning the different import regulations in various countries and in filling in the required forms. Means should be sought to reduce such difficulties and barriers to the effective distribution of reference substances.