Previous reports suggest that prolactin could be one of the factors controlling intestinal mucosal growth. Therefore plasma levels of prolactin have been measured at the time of jejunal biopsy performed for suspicion of celiac disease. One hundred eighty-seven biopsies from 166 children have been reviewed according to histology, age, diagnosis, and plasma prolactin. No difference in the plasma prolactin could be detected among a group of 117 normal biopsies (9.4 +/- 0.4 ng/ml, mean +/- SEM), 31 biopsies with partial atrophy of various degree (9.0 +/- 0.9 ng/ml), and 39 biopsies with flat mucosa (9.1 +/- 0.7 ng/ml), nor could we demonstrate an increase in prolactin according to age and diagnosis (celiac disease before and after treatment, cow's milk protein intolerance, isolated postenteritic syndrome, selective sugar intolerance, and functional gut problems). Prolactinlike material has been detected by immunoperoxidase in the jejunal mucosa. The intracellular granules are located in the infranuclear portion of isolated epithelial cells mainly in the crypts. This material could not be correlated with the corresponding prolactinemias, whatever the histological appearance of the mucosa. These results would suggest that plasma prolactin is not a marker of jejunal regeneration in children. The nature and function(s) of this prolactinlike material remain to be established.