Cow's milk protein intolerance (CMPI) is recognised as an important cause of protean symptoms in infants. There are no tests with enough specificity and sensibility to set up a diagnostic assay. We carried out preliminary study on children suffering from CMPI with the following aims: a) to ascertain the importance of the variation in circulating antibodies to cow's milk proteins in CMPI, b) to establish a useful screening tool to diagnose CMPI. Seventy-four subjects (s.) were studied and divided into four diagnostic groups as follows: Six s. (3 M, 3 F) suffering from CMPI mean age 4.8 +/- 3.9 months, assuming a diet containing cow's milk: I group. Eleven s. (O M, 7 F) suffering from CMPI mean age 7.8 +/- 4.6 months, assuming a cow's milk free diet, for several months (mean 4.5 +/- 1.5): II group. Nine s. (5 M, 4 F) suffering from enteropathies not cow's milk correlated, mean age 18.5 +/- 10.6 months, assuming a diet containing cow's milk: III group. Fourty-eight healthy s. (24 M, 24 F), mean age 10.5 +/- 4.3 months, assuming a diet containing cow's milk.(ABSTRACT TRUNCATED AT 250 WORDS)