VU6036720 (VU 6036720) is the first potent, selective inhibitor of heteromeric Kir4.1/Kir5.1 (KCNJ10/KCNJ16) with IC50 of 0.24 uM.VU6036720 displays >30-fold selective for Kir4.1/5.1 over homomeric Kir4.1 channels, Kir1.1, Kir2.1, Kir2.2, Kir2.3, Kir4.2, Kir6.2/SUR1, Kir6.1/SUR2b and Kir7.1.VU6036720 inhibits Kir4.1/5.1 activity through a reduction of channel open-state probability and single-channel current amplitude, does not induce diuresis in vivo.VU6036720 showwd an IC50 in 3 uM in Tl+ flux assays, approximately 7-times more potent at inhibiting Kir4.1/5.1 than fluoxetine and amitriptyline.VU6036720 represents the current state-of-the-art Kir4.1/5.1 inhibitor that should be useful for probing the functions of Kir4.1/5.1 in vitro and ex vivo.