A comparison was made of clinical signs and provocation tests with the RAST for allergy to dog in eight and cat in twenty patients. Twenty-two had high IgE levels and all gave positive reactions to provocation tests. A commercially available dog epithelium extract gave more positive RASTs than five other dog allergen preparations, and there were no positive reactions to dog serum. The RAST was negative in patients with a low degree of sensitivity. All twenty patients allergic to cat gave positive intracutaneous test reactions and in the RAST the cat epithelial allergen showed 90% agreement with the in vivo findings.