The water-soluble rhenium(I) complex fac-[Re(bpy)(CO)(3)(thp)](+) (1) [CF3SO3- salt; bpy = 2,2'-bipyridine, thp = tris(hydroxymethyl)phosphine] is both strongly luminescent and photoactive toward carbon monoxide release. It is stable in aerated aqueous media, is incorporated into cells from the human prostatic carcinoma cell line PPC-1, and shows no apparent cytotoxicity. Furthermore, the solvated Re(I) photoproduct of CO release (2) is also luminescent, a feature that allows one to track the transformation of 1 to 2 inside such cells using confocal fluorescence microscopy. In this context, 1 is a very promising candidate as a photo-activated CO releasing moiety (photoCORM) with potential therapeutic applications.