Alterations in epidermal growth factor receptor (EGFr) signaling occur in intestinal disorders associated with dysregulated epithelial transport. In the present study we investigated a role for the EGFr in chronic regulation of intestinal epithelial secretory function. Epithelial Cl^- secretion was measured as changes in I_sc across voltage-clamped monolayers of T₈₄ cells in Ussing chambers. Acute treatment of T₈₄ cells with EGF (100 ng/ml; 15 min) chronically enhanced I_sc responses to a broad range of secretagogues. This effect was apparent within 3 hrs, maximal by 6 hrs, and sustained for 24 hrs after treatment with EGF. The Na⁺/K⁺/2Cl^- cotransporter (NKCC1) inhibitor, bumetanide (100 µM), abolished the effect of EGF, indicating increased responses are due to potentiated Cl^- secretion. Neither basal nor agonist-stimulated levels of intracellular Ca²⁺ or PKA activity were altered by EGF, implying the effects of the growth factor are not due to chronic alterations in levels of second messengers. EGF increased expression of NKCC1 with a time course similar to that of its effects on Cl^- secretion. This effect of EGF was maximal after 6 hrs, at which time NKCC1 expression in EGF-treated cells was 199.9 ± 21.9% of that in control cells (n = 21; p<0.005). EGF-induced NKCC1 expression was abolished by actinomycin D and rtPCR analysis demonstrated EGF increased expression of NKCC1 mRNA. These data increase our understanding of mechanisms regulating intestinal fluid and electrolyte transport and reveal a novel role for the EGFr in chronic regulation of epithelial secretory capacity through upregulation of NKCC1 expression.