Pumpdown diagnostics is an economical process in which cement sheath integrity, perforation cluster spacing, and frac plug integrity can be assessed for every frac stage, potentially leading to improvements in stimulation, completion, cementing, and drilling practices. It is based on analyzing wellbore pressure responses occurring at key segments of the wireline pumpdown and perforating operation and correlating the results among multiple frac stages and wells in a field or play. A special requirement is that the ball check is inserted in the frac plug and pumped to seat prior to performing perforating operations. An additional benefit of this process is that selectively establishing injectivity in the most distant perforation cluster can be used to ensure hydrochloric acid coverage across all perforation intervals for uniform reduction in near-wellbore tortuosity. Reviews of pumpdown diagnostics field cases from several unconventional plays have provided a number of insights. Pumpdown diagnostics are time efficient and economical, requiring approximately 15 minutes per frac stage. Evaluating communication to the previous frac stage can serve as a key performance indicator for treatment control or cement sheath integrity. Pumpdown diagnostic results can be more reliable than cement bond log evaluation, and stage isolation characteristics can be strongly affected by cluster spacing.