The procedures for measuring the blood pressure cause emotional reactions, which in turn influence, in a manner which is not to be disregarded, the blood pressure values. In order to evaluate the degree and type of such influence the blood pressure was determined for 3 consecutive days by the same doctor using the same technique in 242 children (150 boys and 92 girls) of a primary school in Bari. The systolic and diastolic values obtained allowed us to categorize the children in to 3 groups in accordance with their individual reactions on occasion of the second and third determination: a) children whose blood pressure went down; b) children whose blood pressure went up; c) children whose blood pressure remained unchanged. The differences of the values obtained between the first and third determination were the most evident; in particular, the PAs had an average reduction of 11.3 mmHg in 68.6% of the subjects, an average increase of 7.7 mmHg in 14.9%, whereas in the remaining 16.5% was unchanged. The PAd had un average reduction of 9.5 mmHg in 51%, an average increase of 7.6 mmHg in 19% and the remaining 30% was unchanged. The heart rate shows a statistically significant reduction of about 4 beats/min. between the first and subsequent determinations, and it is connected with the blood pressure. No correlation was found with the PAd. The variable reactions as a consequence of the repeated determinations could cause an error not to be disregarded, in view of the results obtained from the programs concerning the screening of the PA and of the identification of normal values age related.(ABSTRACT TRUNCATED AT 250 WORDS)