Pharmacological and clinical studies show that standardised willow bark extract is not the only natural form of salicylic acid. Willow bark (Salix spp.) extract has anti-inflammatory activities comparable to higher doses of acetyl-salicylic acid (ASS), and it shows antinociceptive and antipyretic activities. With pharmacologically active doses, no adverse effects on the stomach mucosa were observed. A daily dose of 1572 mg willow bark extract of a proprietary preparation (Assalix standardised to 15.2% salicin; i.e. 240 mg salicin per day) was significantly superior to placebo in patients with osteoarthritis of the hip and the knee, and in patients with exacerbations of chronic low back pain. In two open studies against active treatments as controls, willow bark extract showed advantages against a routinely prescribed treatment scheme of orthopaedic specialists based on non-steroidal antirheumatic drugs and rather similar efficacy to the COX-2-inhibitor rofecoxib.