In the last years the evaluation of IgG against beta-lactoglobulin (beta LG-IgG) has been proposed as reliable test to diagnose Cow's Milk Protein Intolerance (CMPI). This test, associated with other diagnostic tools (such as eosinophilia, hemoccult, RAST, challenge, etc.) showed a good sensibility, but less specificity. In fact antibodies against beta-lactoglobulin were found in other gastrointestinal diseases (coeliac disease, inflammatory bowel diseases, cystic fibrosis, etc.). To determine the specificity of the test some Authors attributed great importance to the laboratory method (IFL, ELISA). They retained IFL more specific. In order to verify the behaviour of the two methods and their concordance we carried out a double bind determination of IgG against beta-lactoglobulin (beta LG-IgG) on serum samples from children affected by CMPI. For this study we chose 16 children, aged from 3 months and 6 years, suffering from CMPI of which 11 with gastrointestinal complaints and 5 from extraintestinal ones. All children were diagnosed on the basis of the following criteria: clinical picture, blood eosinophilia, positivity of hemoccult, amelioration after the withdrawal of cow's milk proteins from the diet, positivity of challenge test. All children at the time of the assessment assuming a diet containing cow's milk proteins. beta LG-IgG were measured using simultaneously immunofluorescent and micro-ELISA methods. The obtained data showed that 12 children (75%) had IgG versus beta-lactoglobulin in the serum. This result was obtained both with IFL and ELISA methods, showing a 100% of concordance.(ABSTRACT TRUNCATED AT 250 WORDS)