Resistive switching memory (also known as RRAM for resistive random access memory) is considered a promising candidate for the next-generation nonvolatile memories.This paper summarizes the electrical characterization methodologies for RRAM performance evaluation and the investigation of resistive switching mechanisms. Some unique issues in RRAM measurements are discussed, including polarity, forming, and switching control. Product-oriented RRAM characterization needs to consider yield, failure mechanisms, and reliability issues, which has only began to be addressed by the RRAM research community.