The controversial phase transitions in barium and bismuth were studied with a manganin coil sensor. The transition in barium proposed at 80 kbars by Bastideetal. was confirmed at 95 kbars. For bismuth, the transition reported first by Bridgman around 45 kbars was confirmed at 40 kbars, but that around 65 kbars could not be detected. To make up theP‐Tdiagram of barium, the confirmed transition and the so‐called high‐Ba transition were traced at elevated temperatures by the resistance anomaly of barium, and the melting points above 90 kbars were determined with a manganin ribbon sensor. The mechanism of the manganin sensor is discussed with regard to the volume change associated with a transition.