This report reviews the 20 years of experience with naturally occurring allergy in dogs and allergic rhesus monkeys. The primate model of allergy is characterized by IgE-mediated cutaneous and respiratory responses to Ascaris antigen. Individual assessments of these monkeys have been carried out over several years and separate populations which are analogous to human IgE-mediated allergic populations defined. These populations are as follows: (1) monkeys which have persistent and consistent IgE-mediated cutaneous and asthmatic responses to Ascaris antigen; (2) monkeys which have cutaneous and airway reactivity to Ascaris antigen but in which the airway reactivity subsides and disappears analogous to a spontaneous remission human asthma, and (3) finally, there is a group of animals with cutaneous reactivity but no asthma analogous to humans with a similar absence of asthma. Within these groups the animals, like humans, have individual variations of severity.