An experiment on electric potential and pressure drop for NaK flow in uniform trnasverse magnetic fields was conducted. A test channel was constructed using 45.3 mm (or 28 mm) I.D. and 1.65 mm thick 304-SS circular pipe in the NaK-Blowdown MHD Experimental Facility of Osaka University. The experimental range covered had a driving gas pressure <8 bar, an applied magnetic flux density: B0=0.3∼1. 75 T, a mean flow velocity of NaK: U0=2∼ 15 m/sec, a Reynolds number Re=8×l04∼6.2×l05 and a Hartmann number: Ha=740∼4150. A theoretical analysis is given on the basis of a uniform-velocity thick-wall model. Good agreement between the theory and the experiment were obtained both for the potential and for the pressure drop, except a small deviation of the experimental pressure drop towards values lying above the theoretical ones in a weak B0 and high U0 region (Ha2/Re <15).