Case histories alone and combined with the results of skin tests and/or the radioallergosorbent test (RAST) were compared with the results of provocation tests in 397 patients with asthma or allergic rhinitis. Case histories often turned out to be doubtful. The agreement between negative histories and negative provocation tests was 77% and that between positive histories and positive provocation tests 64%. When case histories were supported by concordant skin test or RAST results, the agreement with provocation tests increased to about 90%. When a scoring system for the combinations of different diagnostic methods was employed, a 100% agreement with provocation tests was obtained for cases with high scores. It is concluded that by using the case history in conjunction with RAST and/or skin test results, a reliable diagnosis can be achieved, eliminating the necessity of provocation tests.