The magnitude of the effect size of an analgesic intervention can be influenced by several factors, including research design. A key design component is the choice of the primary endpoint. The purpose of this meta-analysis was to compare the assay sensitivity of 2 efficacy paradigms: pain intensity (calculated using summed pain intensity difference [SPID]) and pain relief (calculated using total pain relief [TOTPAR]). A systematic review of the literature was performed to identify acute pain studies that calculated both SPIDs and TOTPARs within the same study. Studies were included in this review if they were randomized, double-blind, placebo-controlled investigations involving medications for postsurgical acute pain and if enough data were provided to calculate TOTPAR and SPID standardized effect sizes.