Guidelines recommend initial blood pressure assessment on both arms, with the higher-reading arm used for future measurements. As simultaneous measurement devices are often unavailable, we evaluated if sequential measurements are appropriate for assessing interarm differences. Blood pressure was measured in Shanghai using an automated system. Consecutive readings were taken with 1-min intervals, beginning with the right followed by the left arm, with a third reading if the difference between the first two exceeded 5 mmHg. In 7838 participants, right arm readings were consistently higher, with mean interarm systolic/diastolic differences of 4.59/1.01 mmHg if two readings on each arm, 6.24/1.45 mmHg if two readings on one and three readings on another arm, and 7.22/1.90 mmHg if three readings on each arm. This sequential measurement approach led to more frequent right arm selection for blood pressure measurement and potential overestimation of the interarm differences. Simultaneous measurements may be needed, but future studies are required to confirm this.