RESUMO
The blood pressure (BP) fluctuation was first noticed in the 18th century. However, its clinical significance did not get attention until recent years. The increase in BP variability (BPV) is possibly more valuable than the increase in BP level for predicting damages in target organs. Moreover, attenuating BPV is more important than decreasing the BP level. However, the concept of BPV was not used in any related guideline for diagnosing, defining, and grading the risk of hypertension, which is due to the understanding of BPV is not profound, and blind areas and misunderstanding still exist in the definition, features, and classification of BPV. In this paper, the doubts and difficulties in studying BPV are analyzed, which may conduce to understand BPV and thus help for the clinical diagnosis and treatment of hypertension.