Cystic fibrosis (CF) is an inherited disease caused by loss of function of the epithelial anion channel cystic fibrosis transmembrane conductance regulator (CFTR).  In addition to pulmonary symptoms commonly associated with CF, many individuals experience gastrointestinal tract complications, caused by impaired salt and water secretion across the intestinal epithelium.  Intestinal organoids grown from rectal biopsies provide a powerful tool to investigate CFTR dysfunction in CF, and aid the identification of small molecule CFTR modulators for personalised medicine (1, 2).  Here we sought an intestinal epithelial cell line suitable for use in the study of CFTR-mediated ion transport in the intestine.  The cell line should possess both the ability to grow as a 2D epithelial monolayer for Ussing chamber studies, and as 3D organoids to optically measure CFTR-mediated lumen expansion. Initial studies using the human colonic LIM1863 cell line, which expresses CFTR and forms organoids resembling colonic crypts (3), revealed that this cell line was unable to form polarised epithelia with a transepithelial resistance when seeded onto permeable filter supports (n>3).  Subsequently a panel of 15 human colorectal adenocarcinoma cell lines were screened to identify a cell line suitable for Ussing chamber and organoid studies. Immunoblotting studies using the anti-CFTR-596 mouse monoclonal antibody (4) detected CFTR in 7 of the 15 cell lines screened.  When the 7 CFTR-expressing cell lines were seeded onto permeable filter supports, only HCA7 (human colonic adenocarcinoma 7) cells developed a transepithelial resistance >0.5 kΩ cm2 (n >20).  To investigate transepithelial ion transport by HCA7 cells, we mounted HCA7 epithelia in Ussing chambers, imposed a large Cl- concentration gradient across the epithelium ([Cl-]basolateral, 149 mM; [Cl-]apical, 14.8 mM), clamped transepithelial voltage at 0 mV and recorded short-circuit current (Isc) continuously (5).  Forskolin (10 µM) stimulated a small increase in Isc that was inhibited by CFTRinh-172 (10 µM) (n >20).  Complementary to these studies, when HCA7 cells were grown in Matrigel for 14 days, they formed organoids with a lumen.  When treated with forskolin (10 µM), organoid lumen increased (n >20).  By contrast, pre-treatment of HCA7 organoids with CFTRinh-172 (10 µM) reduced the lumen expansion stimulated by forskolin (10 µM) (n >20).  We interpret these data to suggest that CFTR mediates cAMP-stimulated ion transport by HCA7 cells.  The data also suggest that HCA7 cells might prove a useful model of intestinal ion transport because they form both polarised epithelia and organoids.