Parathyroid hormone-related protein (PTHrP) is a factor associated with normal development and physiology of the nervous, cardiovascular, immune, reproductive and musculo-skeletal systems in higher vertebrates. It also stimulates whole body calcium uptake in sea bream (Sparus auratus) larvae with an estimated 60% coming from intestinal uptake in seawater. The present study investigated the role of PTHrP in the intestinal calcium transport in the sea bream in vitro. Unidirectional mucosal-to serosal and serosal-to-mucosal ⁴⁵Ca fluxes were measured in vitro in duodenum, hindgut and rectum mounted in Ussing chambers. In symmetric conditions with the same saline bathing apical and basolateral sides of the preparation addition of (1-34) piscine PTHrP (6 nM) to the serosal surface resulted in an increase in calcium fluxes mucose to serose in duodenum and hindgut and a reduction in serose to mucose in the rectum, indicating that different mechanisms are responsive to PTHrP along the intestine. In control asymmetric conditions, with serosal normal and mucosal bathed with a saline similar to composition of the intestinal fluid, there was a net increase in calcium uptake in all regions. The addition of 6 nM (1-34) PTHrP increased net calcium uptake 2 to 3 fold in all regions. The stimulatory effect of PTHrP on net intestinal calcium absorption is consistent with a hypercalcemic role for the hormone. The results support the view that PTHrP, alone or in conjunction with recently identified PTH-like peptides, counteracts in vivo the hypocacemic effects of Stanniocalcin.