Studies were conducted on postpartum and postoperative patients to estimate the dose-response line of fenoprofen and to contrast it with codeine and placebo. The postpartum patients included women with episiotomy pain and with uterine cramping. This mix allowed contrast of ability of the various pain models to distinguish codeine from placebo. The methodology for the studies was single-dose parallel groups design with interviews conducted by trained nurse observers to obtain subjective responses. More than 850 patients participated in the trial. The results indicate that fenoprofen at doses as low as 12.5 mg has analgesic properties. In each of the five studies, the mean value of 100- and/or 200-mg doses of fenoprofen for the variable sum of the pain intensity difference (SPID) was higher than that of 65 mg codeine. The pooled relative potency calculation based on SPID suggests that 100 mg fenoprofen is approximately equivalent to 60 mg codeine. In their ability to distinguish codeine from placebo, patients with uterine cramp, episiotomy, or surgical pain did not appear to differ.