The analgesic effect and the tolerability of alpha-methyl-4-(2-thienyl-carbonyl)phenylacetic acid (suprofen, Suprol) syrup 200 mg and metamizole syrup 500 mg were compared in a randomized single-blind study including hospitalized patients with severe to moderate chronic pain. The 2 treatment groups consisted of 30 subjects each and were homogeneous as to the demographic data. Pain intensity was appreciated by the investigator prior to the treatment and on days 2, 3, and 5 of the study; pain relief was assessed on days 2, 3, and 5 of the therapy. Although pain intensity was on treatment with suprofen more markedly reduced than with metamizole, there was no statistically significant difference between the 2 treatment groups (chi 2-test). The Mann-Whitney test revealed that on days 3 and 5 pain relief with suprofen was significantly superior to that with metamizole. According to the investigator's final global evaluation, suprofen syrup 200 mg had very good to good effect in 70% of the cases, whereas the effectiveness of metamizole was rated good to very good in 44%. Side-effects manifesting themselves as gastric irritation and nausea were recorded for 3 patients on suprofen and 2 subjects on metamizole.