In a study that indicates more definitive investigation is needed, 118 patients with chronic back problems seeking treatment for acute attacks of pain were included in a 4-week randomised double-blinded study on the safety and effectiveness of an extract of Harpagophytum procumbens. Both, the treatment and the placebo were administered in the form of two tablets taken three times per day; the treatment group had a daily consumption equal to 6,000 mg of crude preparation (50 mg harpagoside, the putative active ingredient). The treatment and placebo groups were well matched in physical characteristics; in the severity, duration, nature and accompaniments of their pain; and in laboratory indices of organ system function. 109 patients completed the study. The study was originally designed to measure Harpagophytum's effectiveness by measuring the use of supplementary pain-killer Tramadol over its final 3 weeks. However, this did not differ between the Harpagophytum and placebo groups nor was the consumption closely related to the amount of pain. Further analysis, though, revealed that 9 out of 51 patients who received the extract were pain free at the end of treatment compared to only 1 out of 54 patients who received placebo. A modification of the Arhus index was used as an additional measure, covering the more global impact. The percentage change was greater in those patients who received Harpagophytum extract than in those who received placebo, but inferential testing (Mann Whitney) allowed only 94% degree of confidence that this had not arisen by chance. The Arhus index reduction was based on improvement in pain. This indication of effectiveness, and the absence of demonstrable adverse effects show that more definite clinical studies of Harpagophytum extract will be worthwhile.