Approximately 10% of the 1.25 million species of arthropods, cold-blooded animals with jointed legs and external skeletons, have an impact on public health.  The sheer numbers of arthropods and the variety of habit and habitats occupied by them results in contact between man and animals that can have a negative consequences on the lives of humans.  The first half of this course provides an overview of the ways in which arthropods have a direct impact on human health as accidental, temporary and continuous ecto-parasites of man.  In the second half of the course the role of arthropods as carriers of disease agents are more closely examined.  Arthropods which utilized man as a blood meal source can also function as the carrier of human disease agents.  The fundamentals of the relationships between arthropod vector, the disease pathogen and the human host are examined detailed in the second of two lectures.