The purpose of this manual is to provide basic information on biological toxins to military leaders and health-care providers at all levels to help them make informed decisions on protecting their troops from toxins. Much of the information contained herein will also be of interest to individuals charged with countering domestic and international terrorism. We typically fear what we do not understand. Although understanding toxin poisoning is less useful in a toxin attack than knowledge of cold injury on an Arctic battlefield, information on any threat reduces its potential to harm. I hope that by providing information about the physical characteristics and biological activities of toxins, the threat of toxins will actually be reduced. I did not intend to provide detailed information on individual threat toxins or on medical prevention or treatment. This primer puts toxins in context, attempts to remove the elements of mystery and fear that surround them, and provides general information that will ultimately help leaders make rational decisions, protect their soldiers and win battles.