An examination of the proteinases present in two vety different systems is described, in order to illustrate the diversity in function of this class of enzymes. In the first case we have noted the importance of gut proteinases from the fire ant Solenopsis invicta in relation to the nutritional requirements of the entire colony. In the second we have investigated the properties of endoproteases from both ragweed and mesquite pollen, relative to their role in the development of allergies and asthma. If the function of each type of enzyme(s) is correct, then it is clear that addition of exogenous inhibitors might be useful in a) controlling the infestation associated with the fire ant, and b) reducing the deleterious effects associated with the development of asthma.