It has become a common practice to mail blood specimens collected in glass vials and packed in metal screw-topped containers to private or governmental laboratories for various tests. Basically the postal authorities have no objection to this practice, but complaints have reached the headquarters of the American Medical Association in increasing numbers that the caps of the metal containers are in many instances carelessly screwed on. This results in the glass vial slipping out of the container where it may become broken, so that the specimen stains other mail, to say nothing of the loss to the sender and his patient. In some instances several specimens have come out of their containers in one batch of mail thereby posing an impossible riddle for the postal authorities of trying to figure out which specimen came from which tube. Screwing the caps on securely is apparently not the answer to this problem.