The basic source materials, research strategies, and approach methodologies which were utilized to establish guidelines to aid physicians who examine commercial driver applicants for certification of medical fitness under existing Federal Motor Carrier Safety Regulations are reviewed. The Guide contains (1) the exact language of the medical fitness standards, (2) the range of tasks pertaining to bus and truck drivers which medical examiners must understand to be able to evaluate the degree of physical and mental fitness any applicant has for a job which involves much more than driving, and (3) the regulatory agency's interpretations of the letter-of-the-law and broad postures on medical gray areas. Risk evaluation criteria applicable to diabetic, hypertensive, and/or cardiac applicants are presented.