Despite the frequent use of pain recall ratings in clinical research, there remains doubt about the ability of individuals to accurately recall their pain. In particular, previous research indicates the possibility that the most pain experienced during a recall period and the most recent pain experienced (known as peak and end effects, respectively) might bias recall ratings. The current study used data from a published clinical trial to determine the relative validity of a 24-h recall rating of average post-operative pain and the nature and extent of any biasing influence of peak and end effects on nine separate 24-h recall ratings. The results supported a statistically significant but small biasing influence of both peak and end pain. Also, the influence of peak pain was stronger than that of end pain. However, the biasing impact of both peak and end pain together was very small, suggesting that 24-h recall ratings are adequately valid indicants of average pain for patients participating in post-surgery clinical pain trials.