A new immunoassay system utilizing new automatic instrumentation, new software for evaluation of data, and reagents updated for increased speed and accuracy was evaluated. Six clinical studies included 894 consecutive patients. Major symptoms were rhinoconjunctivitis, asthma, atopic dermatitis, and urticaria. The prevalence of inhalant allergy was 54-69%. Phadiatop, detecting atopic sensitization to common inhalant allergens, agreed with clinical diagnosis in 764/836 cases (91.4%). The clinical sensitivity and specificity were 93% and 89%, respectively. The clinical sensitivity and specificity of UniCAP specific IgE derived from 5170 comparisons with clinical diagnosis were 89% and 91%, respectively. Specific IgE measurements in UniCAP and in the Pharmacia CAP System agreed in 266/274 cases (97%). A comparison of the sensitivity and specificity of Pharmacia CAP System RAST in 1987 and with UniCAP specific IgE in 1995 showed equivalent performance without change of efficacy or degradation of IgE antibodies after 8 years. The systems were equivalent also in terms of measured values (r=0.96, slope=1.12), confirming the standardization of allergens and of assay calibration. UniCAP is an efficient laboratory system for routine diagnostic testing of allergy and a valuable tool for basic studies on allergens and antibodies.