Allergy testing is a useful clinical tool to confirm IgE sensitization, institute avoidance measures, and consider desensitization protocols. The first step in performing allergy testing is the selection of the appropriate allergen panel. While some patients may ask, “Can I be tested for everything?”, a cost-effective approach should include representation of those allergens and allergen classes which are clinically relevant. The use of large panels of allergens can lead to false-positive results and misinterpretation of clinical information. Since the presence of IgE in the absence of symptoms does not indicate clinical allergy, only those allergens to which the patient is exposed and potentially causing symptoms should be tested. The rates of allergy-test positivity vary by country and by region due to climate, humidity, fauna, and individual exposures to animals and pests. This chapter will summarize the important factors used in determining what to test for when performing inhalant allergy testing.