The reliability of total IgE quantitation in predicting atopic states was evaluated in a highly homogeneous group of 315 male subjects between 19 and 22 years of age, in apparent good health. A parallel evaluation of the other major Ig classes (serum IgG, IgA, IgM and salivary IgA) and a series of lung function tests were also performed. Forty-eight subjects (15%) referred history of allergy (41 respiratory and seven cutaneous). Twenty-one percent of these had IgE greater than 440 IU/ml, a value reported as abnormally high. No significant association was found between atopy and any of the lung function tests performed. Clinical history or IgE levels were not related to other Ig classes. Conversely, serum but not salivary IgA levels were significantly reduced in tonsillectomized subjects. From the present data it appears that neither IgE determinations nor performing lung function tests can be considered reliable substitutes for an accurate history and evaluation of clinical parameters.