A survey was undertaken to evaluate the responses to hyposensitization in cats for which a diagnosis of allergic disease was made by assessment of clinical signs and evaluation of allergen-specific immunoglobulin E (IgE) using the radioallergosorbent test (RAST). Eighty-one cases were available for analysis. In 39 cases, a dietary change resulted in some subjective improvement, which usually was minimal; however, some cases had significant improvement. In 75.3% of cases, an improvement of at least 50% was noted and ascribed to a combination of immunotherapy and dietary change, when implemented. The response of the 42 cases in which immunotherapy alone was used or where there was no response to dietary change was broadly similar. Response of the specific dermatological conditions ranged from 93.6% in the case of linear granuloma to 60% in cases where self-induced hair loss was evident. Response also was good in cases of presumed allergic asthma (86.1% improvement) and suspected allergic otitis externa (62.6% improvement). In nine patients, the hyposensitization was discontinued due to lack of response. The results suggest that confirmation of a suspected diagnosis of allergic disease in cats by means of in vitro tests and subsequent therapy with hyposensitization should be a major consideration in feline practice.